mtd: introduce mtd_read interface

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
diff --git a/drivers/mtd/ubi/debug.c b/drivers/mtd/ubi/debug.c
index ab80c0d..e2cdebf 100644
--- a/drivers/mtd/ubi/debug.c
+++ b/drivers/mtd/ubi/debug.c
@@ -216,7 +216,7 @@
 	buf = vmalloc(len);
 	if (!buf)
 		return;
-	err = ubi->mtd->read(ubi->mtd, addr, len, &read, buf);
+	err = mtd_read(ubi->mtd, addr, len, &read, buf);
 	if (err && err != -EUCLEAN) {
 		ubi_err("error %d while reading %d bytes from PEB %d:%d, "
 			"read %zd bytes", err, len, pnum, offset, read);