arm: Move libgcc assembly macros to arch/asm.h

libgcc/macros.h contains some useful assembly macros that are common in
Linux kernel code and facilitate things such as unified ARM/THUMB
assembly. This patch moves it to a more general place where it can be
used by other code as well.

Change-Id: If68e8930aaafa706c54cf9a156fac826b31bb193
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/182178
Reviewed-by: Vincent Palatin <vpalatin@chromium.org>
(cherry picked from commit a780670def94a969829811fa8cf257f12b88f085)
Signed-off-by: Isaac Christensen <isaac.christensen@se-eng.com>
Reviewed-on: http://review.coreboot.org/6917
Tested-by: build bot (Jenkins)
Reviewed-by: David Hendricks <dhendrix@chromium.org>

src/arch/arm/armv7/bootblock.S

@@ -29,9 +29,10 @@
  * MA 02111-1307 USA
  */
 
+#include <arch/asm.h>
+
 .section ".start", "a", %progbits
-.globl _start
-_start:
+ENTRY(_start)
 	/*
 	 * Set the cpu to System mode with IRQ and FIQ disabled. Prefetch/Data
 	 * aborts may happen early and crash before the abort handlers are
@@ -89,6 +90,7 @@ call_bootblock:
 wait_for_interrupt:
 	wfi
 	mov	pc, lr			@ back to my caller
+ENDPROC(_start)
 
 /* we do it this way because it's a 32-bit constant and
  * in some cases too far away to be loaded as just an offset