kernel: fix build error for external kernel.

fixed build error when external kernel is selected from menuconfig.
The patches present in target/linux/generic does not gets applied
to external kernel and build fails while compiling mac82011 &
regmap-core kernel modules. as a fix added check in Makefile for
CONFIG_EXTERNAL_KERNEL_TREE present or not.

Signed-off-by: Sandeep Sheriker Mallikarjun <sandeepsheriker.mallikarjun@microchip.com>

package/kernel/linux/modules/other.mk

@@ -707,11 +707,15 @@ define KernelPackage/regmap
 	   CONFIG_REGMAP_I2C \
 	   CONFIG_SPI=y
   FILES:= \
-	$(LINUX_DIR)/drivers/base/regmap/regmap-core.ko \
 	$(LINUX_DIR)/drivers/base/regmap/regmap-i2c.ko \
 	$(LINUX_DIR)/drivers/base/regmap/regmap-mmio.ko \
 	$(if $(CONFIG_SPI),$(LINUX_DIR)/drivers/base/regmap/regmap-spi.ko)
   AUTOLOAD:=$(call AutoLoad,21,regmap-core regmap-i2c regmap-mmio regmap-spi)
+  ifeq ($(strip $(CONFIG_EXTERNAL_KERNEL_TREE)),"")
+   ifeq ($(strip $(CONFIG_KERNEL_GIT_CLONE_URI)),"")
+    FILES += $(LINUX_DIR)/drivers/base/regmap/regmap-core.ko
+   endif
+  endif
 endef
 
 define KernelPackage/regmap/description

package/kernel/mac80211/Makefile

@@ -1797,11 +1797,16 @@ ifneq ($(CONFIG_PACKAGE_kmod-cfg80211)$(CONFIG_PACKAGE_kmod-lib80211),)
  endef
 endif
 
-define Build/Configure
+#do not Build/Configure for EXTERNAL KERNEL
+ifeq ($(strip $(CONFIG_EXTERNAL_KERNEL_TREE)),"")
+  ifeq ($(strip $(CONFIG_KERNEL_GIT_CLONE_URI)),"")
+    define Build/Configure
 	  cmp $(PKG_BUILD_DIR)/include/linux/ath9k_platform.h $(LINUX_DIR)/include/linux/ath9k_platform.h
 	  cmp $(PKG_BUILD_DIR)/include/linux/ath5k_platform.h $(LINUX_DIR)/include/linux/ath5k_platform.h
 	  cmp $(PKG_BUILD_DIR)/include/linux/rt2x00_platform.h $(LINUX_DIR)/include/linux/rt2x00_platform.h
-endef
+    endef
+  endif
+endif
 
 define Build/Compile
 	$(SH_FUNC) var2file "$(call shvar,mac80211_config)" $(PKG_BUILD_DIR)/.config