Move SIZE_FROM_LOG2_WORDS macro to utils.h

This patch moves the macro SIZE_FROM_LOG2_WORDS() defined in
`arch.h` to `utils.h` as it is utility macro.

Change-Id: Ia8171a226978f053a1ee4037f80142c0a4d21430
diff --git a/bl1/bl1_main.c b/bl1/bl1_main.c
index 3cca176..cb1bc18 100644
--- a/bl1/bl1_main.c
+++ b/bl1/bl1_main.c
@@ -38,6 +38,7 @@
 #include <platform.h>
 #include <platform_def.h>
 #include <smcc_helpers.h>
+#include <utils.h>
 #include "bl1_private.h"
 #include <uuid.h>