[Bug][Build]: Fix the mlnx-platform-api dpkg cache config error (#9705)

Failed to build the mellanox image when dpkg enabled, it has impact on PR checks.

Author: xumia

platform/mellanox/mlnx-platform-api.dep

@@ -1,14 +1,16 @@
 # DPKG FRK
 
-SPATH := $($(SONIC_PLATFORM_API_PY2)_SRC_PATH)
+SPATH := $($(SONIC_PLATFORM_API_PY3)_SRC_PATH)
 SLINKS := $(shell find $(SPATH) -type l -exec echo {} \; | grep -Ev ' ')
 DEP_FILES := $(SONIC_COMMON_FILES_LIST) $(PLATFORM_PATH)/mlnx-platform-api.mk $(PLATFORM_PATH)/mlnx-platform-api.dep
 DEP_FILES += $(SONIC_COMMON_BASE_FILES_LIST)
 DEP_FILES += $(shell git ls-files -- $(SPATH) | grep -Ev ' ')
 
-$(SONIC_PLATFORM_API_PY2)_CACHE_MODE := GIT_CONTENT_SHA
-$(SONIC_PLATFORM_API_PY2)_DEP_FLAGS := $(SONIC_COMMON_FLAGS_LIST)
-$(SONIC_PLATFORM_API_PY2)_DEP_FILES := $(filter-out $(SLINKS),$(DEP_FILES))
+ifeq ($(ENABLE_PY2_MODULES), y)
+    $(SONIC_PLATFORM_API_PY2)_CACHE_MODE := GIT_CONTENT_SHA
+    $(SONIC_PLATFORM_API_PY2)_DEP_FLAGS := $(SONIC_COMMON_FLAGS_LIST)
+    $(SONIC_PLATFORM_API_PY2)_DEP_FILES := $(filter-out $(SLINKS),$(DEP_FILES))
+endif
 
 $(SONIC_PLATFORM_API_PY3)_CACHE_MODE := GIT_CONTENT_SHA
 $(SONIC_PLATFORM_API_PY3)_DEP_FLAGS := $(SONIC_COMMON_FLAGS_LIST)