qcacld-3.0: add support for wlan config override

Introduce a new Kbuild option 'WLAN_CFG_OVERRIDE' to override
wlan configurations.
Value of this option is a list, which includes the config items
those need to override, its pattern is as below:
WLAN_CFG_OVERRIDE="WLAN_CFG_1=n WLAN_CFG_2=y WLAN_CFG_3=n"

For LA build, it makes use of this Kbuild option, and introduces
new android build options for different products:
  WLAN_CFG_OVERRIDE_wlan: for single wlan driver case.
  WLAN_CFG_OVERRIDE_<chip>: for multiple wlan drivers case, for
    example WLAN_CFG_OVERRIDE_qca6390 and WLAN_CFG_OVERRIDE_qca6174.

Change-Id: I8e062c62d36e076a79032a47aa04501d4543a9c8
CRs-Fixed: 2515905

Android.mk

@@ -112,6 +112,10 @@ KBUILD_OPTIONS += MODNAME=$(LOCAL_MOD_NAME)
 KBUILD_OPTIONS += BOARD_PLATFORM=$(TARGET_BOARD_PLATFORM)
 KBUILD_OPTIONS += $(WLAN_SELECT)
 
+ifneq ($(WLAN_CFG_OVERRIDE_$(LOCAL_DEV_NAME)),)
+KBUILD_OPTIONS += WLAN_CFG_OVERRIDE="$(WLAN_CFG_OVERRIDE_$(LOCAL_DEV_NAME))"
+endif
+
 include $(CLEAR_VARS)
 LOCAL_MODULE              := $(WLAN_CHIPSET)_$(LOCAL_DEV_NAME).ko
 LOCAL_MODULE_KBUILD_NAME  := $(LOCAL_MOD_NAME).ko