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/mtdchar.c b/drivers/mtd/mtdchar.c
index 92da621..64efcbf 100644
--- a/drivers/mtd/mtdchar.c
+++ b/drivers/mtd/mtdchar.c
@@ -867,10 +867,7 @@
 
 		if (copy_from_user(&offs, argp, sizeof(loff_t)))
 			return -EFAULT;
-		if (!mtd->block_isbad)
-			ret = -EOPNOTSUPP;
-		else
-			return mtd_block_isbad(mtd, offs);
+		return mtd_block_isbad(mtd, offs);
 		break;
 	}