UBI: use debugfs for the extra checks knobs

This patch introduces debugfs support to UBI. All the UBI stuff is kept in the
"ubi" debugfs directory, which contains per-UBI device "ubi/ubiX"
sub-directories, containing debugging files. This file also creates
"ubi/ubiX/chk_gen" and "ubi/ubiX/chk_io" knobs for switching general and I/O
extra checks on and off. And it removes the 'debug_chks' UBI module parameters.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
diff --git a/drivers/mtd/ubi/wl.c b/drivers/mtd/ubi/wl.c
index d5076d2..bf13ca2 100644
--- a/drivers/mtd/ubi/wl.c
+++ b/drivers/mtd/ubi/wl.c
@@ -1582,7 +1582,7 @@
 	long long read_ec;
 	struct ubi_ec_hdr *ec_hdr;
 
-	if (!(ubi_chk_flags & UBI_CHK_GEN))
+	if (!ubi->dbg->chk_gen)
 		return 0;
 
 	ec_hdr = kzalloc(ubi->ec_hdr_alsize, GFP_NOFS);
@@ -1623,7 +1623,7 @@
 				     struct ubi_wl_entry *e,
 				     struct rb_root *root)
 {
-	if (!(ubi_chk_flags & UBI_CHK_GEN))
+	if (!ubi->dbg->chk_gen)
 		return 0;
 
 	if (in_wl_tree(e, root))
@@ -1649,7 +1649,7 @@
 	struct ubi_wl_entry *p;
 	int i;
 
-	if (!(ubi_chk_flags & UBI_CHK_GEN))
+	if (!ubi->dbg->chk_gen)
 		return 0;
 
 	for (i = 0; i < UBI_PROT_QUEUE_LEN; ++i)