arm: Support pre-relocation malloc()

Add support for re-relocation malloc() in arm's start-up code.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/README b/README
index f704eb3..31e08fc 100644
--- a/README
+++ b/README
@@ -3752,6 +3752,9 @@
 		Pre-relocation malloc() is only supported on sandbox
 		at present but is fairly easy to enable for other archs.
 
+		Pre-relocation malloc() is only supported on ARM at present
+		but is fairly easy to enable for other archs.
+
 - CONFIG_SYS_BOOTM_LEN:
 		Normally compressed uImages are limited to an
 		uncompressed size of 8 MBytes. If this is not enough,