common: env_flags: fix loop condition when using env_flags_varaccess_mask

We should use ARRAY_SIZE, but not sizeof. The size of
env_flags_varaccess_mask is 16bytes, but we only need 4 loops.
If using 16 as the end condition, we may access memory that
not belong to array env_flags_varaccess_mask.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Cc: Joe Hershberger <joe.hershberger@ni.com>
Cc: York Sun <yorksun@freescale.com>
Cc: Simon Glass <sjg@chromium.org>
Cc: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>
diff --git a/common/env_flags.c b/common/env_flags.c
index 7719355..9c3aed1 100644
--- a/common/env_flags.c
+++ b/common/env_flags.c
@@ -152,7 +152,7 @@
 {
 	int i;
 
-	for (i = 0; i < sizeof(env_flags_varaccess_mask); i++)
+	for (i = 0; i < ARRAY_SIZE(env_flags_varaccess_mask); i++)
 		if (env_flags_varaccess_mask[i] ==
 		    (binflags & ENV_FLAGS_VARACCESS_BIN_MASK))
 			return (enum env_flags_varaccess)i;