mtd: onenand: add missing check

Coverity has reported that inside the function "onenand_block_by_block_erase()"
in onenand_base.c, we should add a check to prevent the incrementing of
possible NULL value for "region"

Signed-off-by: Maxin B. John <john.maxin@nokia.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
diff --git a/drivers/mtd/onenand/onenand_base.c b/drivers/mtd/onenand/onenand_base.c
index d27f93b..289ee3b 100644
--- a/drivers/mtd/onenand/onenand_base.c
+++ b/drivers/mtd/onenand/onenand_base.c
@@ -2453,7 +2453,7 @@
 		len -= block_size;
 		addr += block_size;
 
-		if (addr == region_end) {
+		if (region && addr == region_end) {
 			if (!len)
 				break;
 			region++;