UBI: Fastmap: Enhance fastmap checking

Don't update the fastmap upon detach if fastmap checking is enabled.
This is poor men's power cut testing feature. :-)
Signed-off-by: Richard Weinberger <richard@nod.at>

drivers/mtd/ubi/build.c

@@ -1114,7 +1114,10 @@ int ubi_detach_mtd_dev(int ubi_num, int anyway)
 	ubi_msg(ubi, "detaching mtd%d", ubi->mtd->index);
 #ifdef CONFIG_MTD_UBI_FASTMAP
 	/* If we don't write a new fastmap at detach time we lose all
-	 * EC updates that have been made since the last written fastmap. */
+	 * EC updates that have been made since the last written fastmap.
+	 * In case of fastmap debugging we omit the update to simulate an
+	 * unclean shutdown. */
+	if (!ubi_dbg_chk_fastmap(ubi))
 		ubi_update_fastmap(ubi);
 #endif
 	/*