Move ARCH_* from board/Kconfig to cpu or soc Kconfig.

CONFIG_ARCH is a property of the cpu or soc rather than a property of the
board. Hence, move ARCH_* from every single board to respective cpu or soc
Kconfigs. Also update abuild to ignore ARCH_ from mainboards.

Change-Id: I6ec1206de5a20601c32d001a384a47f46e6ce479
Signed-off-by: Furquan Shaikh <furquan@google.com>
Reviewed-on: http://review.coreboot.org/5570
Tested-by: build bot (Jenkins)
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>

src/cpu/Kconfig

@@ -1,17 +1,12 @@
 # Warning: This file is included whether or not the if is here.
 # The if controls how the evaluation occurs.
 # (See also src/Kconfig)
-if ARCH_ARMV7
 
 source src/cpu/allwinner/Kconfig
 source src/cpu/armltd/Kconfig
 source src/cpu/samsung/Kconfig
 source src/cpu/ti/Kconfig
 
-endif	# ARCH_ARM
-
-if ARCH_X86
-
 source src/cpu/amd/Kconfig
 source src/cpu/dmp/Kconfig
 source src/cpu/intel/Kconfig
@@ -19,6 +14,8 @@ source src/cpu/via/Kconfig
 source src/cpu/qemu-x86/Kconfig
 source src/cpu/x86/Kconfig
 
+if ARCH_X86
+
 config CACHE_AS_RAM
 	bool
 	default !ROMCC