mtd: introduce mtd_has_oob helper

We are working in the direction of making sure that MTD clients to not
use 'mtd->func' pointers directly. In some places we want to know if
OOB operations are supported by an MTD device. Introduce 'mtd_has_oob()'
helper for these purposes.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
diff --git a/include/linux/mtd/mtd.h b/include/linux/mtd/mtd.h
index f0dd5a30..4787015 100644
--- a/include/linux/mtd/mtd.h
+++ b/include/linux/mtd/mtd.h
@@ -454,6 +454,11 @@
 	return do_div(sz, mtd->writesize);
 }
 
+static inline int mtd_has_oob(const struct mtd_info *mtd)
+{
+	return mtd->read_oob && mtd->write_oob;
+}
+
 	/* Kernel-side ioctl definitions */
 
 struct mtd_partition;