m68k: Use cc-cross-prefix

The cc-cross-prefix is new and developed on request from Geert Uytterhoeven.

With cc-cross-prefix it is now much easier to have a few default cross compile
prefixes and defaulting to none - if none of them were present.  ARCH
maintainers are expected to pick up this feature soon.
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Andreas Schwab <schwab@suse.de>
Cc: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/m68k/Makefile

@@ -13,16 +13,15 @@
 # Copyright (C) 1994 by Hamish Macdonald
 #
 
-# test for cross compiling
-COMPILE_ARCH = $(shell uname -m)
-
 # override top level makefile
 AS += -m68020
 LDFLAGS := -m m68kelf
 LDFLAGS_MODULE += -T $(srctree)/arch/m68k/kernel/module.lds
-ifneq ($(COMPILE_ARCH),$(ARCH))
-	# prefix for cross-compiling binaries
-	CROSS_COMPILE = m68k-linux-gnu-
+ifneq ($(SUBARCH),$(ARCH))
+	ifeq ($(CROSS_COMPILE),)
+		CROSS_COMPILE := $(call cc-cross-prefix, \
+			m68k-linux-gnu- m68k-linux- m68k-unknown-linux-gnu-)
+	endif
 endif
 
 ifdef CONFIG_SUN3