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>

drivers/mtd/ubi/attach.c

@@ -1419,7 +1419,7 @@ int ubi_attach(struct ubi_device *ubi, int force_scan)
 		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();