arm: Remove some pointless CFLAGS

This patch removes the -ffixed-r8 CFLAG from the coreboot and libpayload
Makefiles. This seems to be a relic from U-Boot, which uses that
register to keep it's global data structure pointer. There's no reason
for us to throw away a perfectly fine register on this already pretty
constrained architecture.

Also removed a config.h inclusion from the Makefile because that should
really be done inside the C files.

Change-Id: Ia176c0f323c1be07cddf88fa5488788786a27cdf
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/177110
Reviewed-by: Gabe Black <gabeblack@chromium.org>
(cherry picked from commit 2a81112abde284ba09020db6afa363169911a7f6)
Signed-off-by: Isaac Christensen <isaac.christensen@se-eng.com>
Reviewed-on: http://review.coreboot.org/6880
Tested-by: build bot (Jenkins)
Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

payloads/libpayload/arch/arm/Makefile.inc

@@ -27,7 +27,7 @@
 ## SUCH DAMAGE.
 ##
 
-CFLAGS += -ffixed-r8 -mfloat-abi=hard -marm -mabi=aapcs-linux -march=armv7-a
+CFLAGS += -mfloat-abi=hard -marm -mabi=aapcs-linux -march=armv7-a
 
 head.o-y += head.S
 libc-y += main.c sysinfo.c