[mellanox]: Fix sysfs path for PSU devices in psuutil plugin (#2143)

Snmp container needs to access the PSU path, but /bsp doesn't mount
into the container, so need to use the real path rather than a symlink.

Signed-off-by: Kevin Wang <kevinw@mellanox.com>

device/mellanox/x86_64-mlnx_msn2010-r0/plugins/psuutil.py

@@ -20,10 +20,14 @@ class PsuUtil(PsuBase):
 
     def __init__(self):
         PsuBase.__init__(self)
-
-        self.psu_path = "/bsp/module/"
-        self.psu_presence = "psu{}_pwr_status"
-        self.psu_oper_status = "psu{}_pwr_status"
+        self.psu_path = ""
+        for index in range(0, 100):
+            hwmon_path = "/sys/devices/platform/mlxplat/mlxreg-hotplug/hwmon/hwmon{}/".format(index)
+            if os.path.exists(hwmon_path):
+                self.psu_path = hwmon_path
+                break
+        self.psu_presence = "pwr{}"
+        self.psu_oper_status = "pwr{}"
 
     def get_num_psus(self):
         """

device/mellanox/x86_64-mlnx_msn2100-r0/plugins/psuutil.py

@@ -21,9 +21,14 @@ class PsuUtil(PsuBase):
     def __init__(self):
         PsuBase.__init__(self)
 
-        self.psu_path = "/bsp/module/"
-        self.psu_presence = "psu{}_status"
-        self.psu_oper_status = "psu{}_pwr_status"
+        self.psu_path = ""
+        for index in range(0, 100):
+            hwmon_path = "/sys/devices/platform/mlxplat/mlxreg-hotplug/hwmon/hwmon{}/".format(index)
+            if os.path.exists(hwmon_path):
+                self.psu_path = hwmon_path
+                break
+        self.psu_presence = "pwr{}"
+        self.psu_oper_status = "pwr{}"
 
     def get_num_psus(self):
         """

device/mellanox/x86_64-mlnx_msn2410-r0/plugins/psuutil.py

@@ -21,9 +21,14 @@ class PsuUtil(PsuBase):
     def __init__(self):
         PsuBase.__init__(self)
 
-        self.psu_path = "/bsp/module/"
-        self.psu_presence = "psu{}_status"
-        self.psu_oper_status = "psu{}_pwr_status"
+        self.psu_path = ""
+        for index in range(0, 100):
+            hwmon_path = "/sys/devices/platform/mlxplat/mlxreg-hotplug/hwmon/hwmon{}/".format(index)
+            if os.path.exists(hwmon_path):
+                self.psu_path = hwmon_path
+                break
+        self.psu_presence = "psu{}"
+        self.psu_oper_status = "pwr{}"
 
     def get_num_psus(self):
         """

device/mellanox/x86_64-mlnx_msn2700-r0/plugins/psuutil.py

@@ -21,9 +21,14 @@ class PsuUtil(PsuBase):
     def __init__(self):
         PsuBase.__init__(self)
 
-        self.psu_path = "/bsp/module/"
-        self.psu_presence = "psu{}_status"
-        self.psu_oper_status = "psu{}_pwr_status"
+        self.psu_path = ""
+        for index in range(0, 100):
+            hwmon_path = "/sys/devices/platform/mlxplat/mlxreg-hotplug/hwmon/hwmon{}/".format(index)
+            if os.path.exists(hwmon_path):
+                self.psu_path = hwmon_path
+                break
+        self.psu_presence = "psu{}"
+        self.psu_oper_status = "pwr{}"
 
     def get_num_psus(self):
         """

device/mellanox/x86_64-mlnx_msn2740-r0/plugins/psuutil.py

@@ -20,10 +20,14 @@ class PsuUtil(PsuBase):
 
     def __init__(self):
         PsuBase.__init__(self)
-
-        self.psu_path = "/bsp/module/"
-        self.psu_presence = "psu{}_status"
-        self.psu_oper_status = "psu{}_pwr_status"
+        self.psu_path = ""
+        for index in range(0, 100):
+            hwmon_path = "/sys/devices/platform/mlxplat/mlxreg-hotplug/hwmon/hwmon{}/".format(index)
+            if os.path.exists(hwmon_path):
+                self.psu_path = hwmon_path
+                break
+        self.psu_presence = "psu{}"
+        self.psu_oper_status = "pwr{}"
 
     def get_num_psus(self):
         """