armv7: clean but do not invalidate caches between stages

This cleans the caches without invalidating them between stages. The
dcache content should still be valid when the next stage begins, so
we should see a small performance gain.

(thanks to gabeblack for pointing this out)

Signed-off-by: David Hendricks <dhendrix@chromium.org>
BUG=none
BRANCH=none
TEST=built and booted on pit

Change-Id: Ie18d163f3a78e2786e9fbc7479c8bd896b8ac3aa
Reviewed-on: https://gerrit.chromium.org/gerrit/66119
Commit-Queue: David Hendricks <dhendrix@chromium.org>
Tested-by: David Hendricks <dhendrix@chromium.org>
Reviewed-by: Ronald G. Minnich <rminnich@chromium.org>

src/arch/armv7/stages.c

@@ -52,7 +52,7 @@ void stage_exit(void *addr)
 	/* make sure any code we installed is written to memory. Not all ARM have
 	 * unified caches.
 	 */
-	dcache_clean_invalidate_all();
+	dcache_clean_all();
 	/* Because most stages copy code to memory, it's a safe and hygienic thing
 	 * to flush the icache here.
 	 */