mtd: introduce mtd_write_user_prot_reg 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 6aa3fb4..d888170 100644
--- a/drivers/mtd/mtdchar.c
+++ b/drivers/mtd/mtdchar.c
@@ -314,7 +314,8 @@
 				ret = -EOPNOTSUPP;
 				break;
 			}
-			ret = mtd->write_user_prot_reg(mtd, *ppos, len, &retlen, kbuf);
+			ret = mtd_write_user_prot_reg(mtd, *ppos, len,
+						      &retlen, kbuf);
 			break;
 
 		case MTD_FILE_MODE_RAW: