UBI: Fastmap: Fall back to scanning mode after ECC error

If we encounter an uncorrectable ECC error while scanning for the fastmap
UBI must not fail hard. Instead fall back to scanning mode.

Reported-by: Alexander Block <Alexander.Block@continental-corporation.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
diff --git a/drivers/mtd/ubi/attach.c b/drivers/mtd/ubi/attach.c
index 42d465a..68eea5b 100644
--- a/drivers/mtd/ubi/attach.c
+++ b/drivers/mtd/ubi/attach.c
@@ -1419,7 +1419,7 @@
 		err = scan_all(ubi, ai, 0);
 	else {
 		err = scan_fast(ubi, &ai);
-		if (err > 0) {
+		if (err > 0 || mtd_is_eccerr(err)) {
 			if (err != UBI_NO_FASTMAP) {
 				destroy_ai(ai);
 				ai = alloc_ai();