[slave.mk]: Adding support to specify debs dependencies for python-de…

…bs package. (#4849)

**- How I did it**
added below line:
$$(addsuffix -install,$$(addprefix $(DEBS_PATH)/,$$($$*_DEBS_DEPENDS))) \

**- How to verify it**
Added below dependencies in sonic-utils
```
SONIC_UTILS = python-sonic-utilities_1.2-1_all.deb
$(SONIC_UTILS)_SRC_PATH = $(SRC_PATH)/sonic-utilities
$(SONIC_UTILS)_DEBS_DEPENDS = $(LIBYANG) $(LIBYANG_CPP) $(LIBYANG_PY2) \  <<<<<<<<<<<
                                     $(LIBYANG_PY3)
$(SONIC_UTILS)_WHEEL_DEPENDS = $(SONIC_CONFIG_ENGINE) $(SONIC_YANG_MGMT_PY)
SONIC_PYTHON_STDEB_DEBS += $(SONIC_UTILS)
```
Build the PKGs successfully.

Signed-off-by: Praveen Chaudhary pchaudhary@linkedin.com

slave.mk

@@ -501,6 +501,7 @@ $(SONIC_INSTALL_TARGETS) : $(DEBS_PATH)/%-install : .platform $$(addsuffix -inst
 #     $(SOME_NEW_DEB)_DEPENDS = $(SOME_OTHER_DEB1) $(SOME_OTHER_DEB2) ...
 #     SONIC_PYTHON_STDEB_DEBS += $(SOME_NEW_DEB)
 $(addprefix $(PYTHON_DEBS_PATH)/, $(SONIC_PYTHON_STDEB_DEBS)) : $(PYTHON_DEBS_PATH)/% : .platform \
+		$$(addsuffix -install,$$(addprefix $(DEBS_PATH)/,$$($$*_DEBS_DEPENDS))) \
 		$$(addsuffix -install,$$(addprefix $(PYTHON_DEBS_PATH)/,$$($$*_DEPENDS))) \
 		$$(addsuffix -install,$$(addprefix $(PYTHON_WHEELS_PATH)/,$$($$*_WHEEL_DEPENDS))) \
 		$(call dpkg_depend,$(PYTHON_DEBS_PATH)/%.dep)