Remove \n from the end of fs_path in ONIEUpdater (#12465)

This fixes the following error

```
admin@sonic:~$ sudo fwutil show status
mount: /mnt/onie-fs: special device /dev/sda2
 does not exist.
Error: Command '['mount', '-n', '-r', '-t', 'ext4', '/dev/sda2\n', '/mnt/onie-fs']' returned non-zero exit status 32.. Aborting...
Aborted!
admin@sonic:~$ sudo vi /usr/local/lib/python3.9/dist-packages/sonic_platform/

```
Seems like #11877 the rstrip('\n') was removed. Probably by mistake.

Signed-off-by: Stephen Sun <stephens@nvidia.com>

platform/mellanox/mlnx-platform-api/sonic_platform/component.py

@@ -172,7 +172,7 @@ def __mount_onie_fs(self):
         cmd1 = ['fdisk', '-l']
         cmd2 = ['grep', 'ONIE boot']
         cmd3 = ['awk', '{print $1}']
-        fs_path = check_output_pipe(cmd1, cmd2, cmd3)
+        fs_path = check_output_pipe(cmd1, cmd2, cmd3).rstrip('\n')
 
         os.mkdir(fs_mountpoint)
         cmd = ["mount", "-n", "-r", "-t", "ext4", fs_path, fs_mountpoint]