mtd: introduce mtd_can_have_bb helper

This patch introduces new 'mtd_can_have_bb()' helper function which checks
whether the flash can have bad eraseblocks. Then it changes all the
direct 'mtd->block_isbad' use cases with 'mtd_can_have_bb()'.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
diff --git a/drivers/mtd/redboot.c b/drivers/mtd/redboot.c
index 09bb81e..48970c1 100644
--- a/drivers/mtd/redboot.c
+++ b/drivers/mtd/redboot.c
@@ -78,7 +78,7 @@
 
 	if ( directory < 0 ) {
 		offset = master->size + directory * master->erasesize;
-		while (master->block_isbad && 
+		while (mtd_can_have_bb(master) &&
 		       mtd_block_isbad(master, offset)) {
 			if (!offset) {
 			nogood:
@@ -89,7 +89,7 @@
 		}
 	} else {
 		offset = directory * master->erasesize;
-		while (master->block_isbad && 
+		while (mtd_can_have_bb(master) &&
 		       mtd_block_isbad(master, offset)) {
 			offset += master->erasesize;
 			if (offset == master->size)