Fix sonic-config low dpkg hit rate issue (#12244)

Why I did it
When sending a PR only CI change, as expected, the target target/python-wheels/buster/sonic_config_engine-1.0-py2-none-any.whl should be from the cache, because the depended files were not changed, but it rebuilt.

How I did it
Sort the files by name.

rules/sonic-config.dep

@@ -4,7 +4,7 @@ SPATH       := $($(SONIC_CONFIG_ENGINE_PY3)_SRC_PATH)
 DEP_FILES   := $(SONIC_COMMON_FILES_LIST) rules/sonic-config.mk rules/sonic-config.dep   
 DEP_FILES   += $(SONIC_COMMON_BASE_FILES_LIST)
 DEP_FILES   += $(shell git ls-files $(SPATH))
-DEP_FILES   += files/image_config/interfaces/interfaces.j2 dockers/docker-orchagent/ports.json.j2 dockers/docker-dhcp-relay/wait_for_intf.sh.j2 dockers/docker-dhcp-relay/docker-dhcp-relay.supervisord.conf.j2 dockers/docker-lldp/lldpd.conf.j2 dockers/docker-orchagent/ipinip.json.j2 $(shell find device -type f) files/build_templates/qos_config.j2 dockers/docker-orchagent/switch.json.j2 dockers/docker-orchagent/vxlan.json.j2 files/image_config/constants/constants.yml
+DEP_FILES   += files/image_config/interfaces/interfaces.j2 dockers/docker-orchagent/ports.json.j2 dockers/docker-dhcp-relay/wait_for_intf.sh.j2 dockers/docker-dhcp-relay/docker-dhcp-relay.supervisord.conf.j2 dockers/docker-lldp/lldpd.conf.j2 dockers/docker-orchagent/ipinip.json.j2 $(shell find device -type f | sort) files/build_templates/qos_config.j2 dockers/docker-orchagent/switch.json.j2 dockers/docker-orchagent/vxlan.json.j2 files/image_config/constants/constants.yml
 
 ifeq ($(ENABLE_PY2_MODULES), y)
     $(SONIC_CONFIG_ENGINE_PY2)_CACHE_MODE  := GIT_CONTENT_SHA