libpayload: Initial ARMv7 port

This compiles, but it's not tested yet.

Change-Id: I2f73a814649aa36c39af3e77cefd8a968671f5c0
Signed-off-by: Stefan Reinauer <reinauer@google.com>
Reviewed-on: http://review.coreboot.org/2035
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

payloads/libpayload/libc/time.c

@@ -118,7 +118,7 @@ static void gettimeofday_init(void)
 }
 #endif
 #endif
-#ifdef CONFIG_TARGET_POWERPC
+#ifdef CONFIG_ARCH_POWERPC
 static void update_clock(void)
 {
 }