mtd: nand: do not scan BBT after scrub

Currently, "nand scrub" runs chip->scan_bbt at the end of
nand_erase_opts() even if NAND_SKIP_BBTSCAN flag is set.

It violates the intention of NAND_SKIP_BBTSCAN.

Move NAND_SKIP_BBTSCAN flag check to nand_block_checkbad() so that
chip->scan_bbt() is never run if NAND_SKIP_BBTSCAN is set.

Also, unset NAND_BBT_SCANNED flag instead of running chip->scan_bbt()
right after scrub.  We can be lazier here because the BBT is scanned
at the next call of nand_block_checkbad().

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cc: Scott Wood <scottwood@freescale.com>
diff --git a/drivers/mtd/nand/nand_util.c b/drivers/mtd/nand/nand_util.c
index 024f6fb..afdd160 100644
--- a/drivers/mtd/nand/nand_util.c
+++ b/drivers/mtd/nand/nand_util.c
@@ -91,6 +91,7 @@
 			kfree(chip->bbt);
 		}
 		chip->bbt = NULL;
+		chip->options &= ~NAND_BBT_SCANNED;
 	}
 
 	for (erased_length = 0;
@@ -179,9 +180,6 @@
 	if (!opts->quiet)
 		printf("\n");
 
-	if (opts->scrub)
-		chip->scan_bbt(meminfo);
-
 	return 0;
 }