ubi: fastmap: fix spelling mistake: "invalidiate" -> "invalidate"

Trivial fix to spelling mistake in ubi_err error message
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Reviewed-by: NBoris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: NRichard Weinberger <richard@nod.at>

drivers/mtd/ubi/fastmap.c

@@ -1667,7 +1667,7 @@ int ubi_update_fastmap(struct ubi_device *ubi)
 
 	ret = invalidate_fastmap(ubi);
 	if (ret < 0) {
-		ubi_err(ubi, "Unable to invalidiate current fastmap!");
+		ubi_err(ubi, "Unable to invalidate current fastmap!");
 		ubi_ro_mode(ubi);
 	} else {
 		return_fm_pebs(ubi, old_fm);