mtd: introduce mtd_get_unmapped_area 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/mtdchar.c b/drivers/mtd/mtdchar.c
index 41d64ff..c51f04a 100644
--- a/drivers/mtd/mtdchar.c
+++ b/drivers/mtd/mtdchar.c
@@ -1135,7 +1135,7 @@
 		if (offset > mtd->size - len)
 			return (unsigned long) -EINVAL;
 
-		return mtd->get_unmapped_area(mtd, len, offset, flags);
+		return mtd_get_unmapped_area(mtd, len, offset, flags);
 	}
 
 	/* can't map directly */