kernel.mk: Refactor LINUX_KARCH affectation

Switch to a dumber implementation that will be easier to maintain in the long
run, with only if statements instead of having nested subst calls.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

SVN-Revision: 43671

include/kernel.mk

@@ -64,13 +64,20 @@ endif
 
 ifneq (,$(findstring uml,$(BOARD)))
   LINUX_KARCH=um
+else ifneq (,$(findstring $(ARCH), aarch64 aarch64_be))
+  LINUX_KARCH := arm64
+else ifneq (,$(findstring $(ARCH), armeb))
+  LINUX_KARCH := arm
+else ifneq (,$(findstring $(ARCH), mipsel mips64 mips64el))
+  LINUX_KARCH := mips
+else ifneq (,$(findstring $(ARCH), sh2 sh3 sh4))
+  LINUX_KARCH := sh
+else ifneq (,$(findstring $(ARCH), i386))
+  LINUX_KARCH := x86
 else
-  ifeq (,$(LINUX_KARCH))
-    LINUX_KARCH=$(strip $(subst i386,x86,$(subst armeb,arm,$(subst mipsel,mips,$(subst mips64,mips,$(subst mips64el,mips,$(subst sh2,sh,$(subst sh3,sh,$(subst sh4,sh,$(subst aarch64,arm64,$(subst aarch64_be,arm64,$(ARCH))))))))))))
-  endif
+  LINUX_KARCH := $(ARCH)
 endif
 
-
 define KernelPackage/Defaults
   FILES:=
   AUTOLOAD:=