UBIFS: introduce helper functions for debugging checks and tests

This patch introduces helper functions for all debugging checks, so instead of
doing

if (!(ubifs_chk_flags & UBIFS_CHK_GEN))

we now do

if (!dbg_is_chk_gen(c))

This is a preparation to further changes where the flags will go away, and
we'll need to only change the helper functions, but the code which utilizes
them won't be touched.

At the same time this patch removes 'dbg_force_in_the_gaps()',
'dbg_force_in_the_gaps_enabled()', and dbg_failure_mode helpers for
consistency.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
diff --git a/fs/ubifs/lpt_commit.c b/fs/ubifs/lpt_commit.c
index 254e8d3..f8e286b 100644
--- a/fs/ubifs/lpt_commit.c
+++ b/fs/ubifs/lpt_commit.c
@@ -1640,7 +1640,7 @@
 	int ret;
 	void *buf, *p;
 
-	if (!(ubifs_chk_flags & UBIFS_CHK_LPROPS))
+	if (!dbg_is_chk_lprops(c))
 		return 0;
 
 	buf = p = __vmalloc(c->leb_size, GFP_NOFS, PAGE_KERNEL);
@@ -1711,7 +1711,7 @@
 {
 	int lnum, err, i, cnt;
 
-	if (!(ubifs_chk_flags & UBIFS_CHK_LPROPS))
+	if (!dbg_is_chk_lprops(c))
 		return 0;
 
 	/* Bring the entire tree into memory */
@@ -1754,7 +1754,7 @@
 	long long free = 0;
 	int i;
 
-	if (!(ubifs_chk_flags & UBIFS_CHK_LPROPS))
+	if (!dbg_is_chk_lprops(c))
 		return 0;
 
 	for (i = 0; i < c->lpt_lebs; i++) {
@@ -1796,7 +1796,7 @@
 	long long chk_lpt_sz, lpt_sz;
 	int err = 0;
 
-	if (!(ubifs_chk_flags & UBIFS_CHK_LPROPS))
+	if (!dbg_is_chk_lprops(c))
 		return 0;
 
 	switch (action) {
@@ -2019,7 +2019,7 @@
 	struct ubifs_lpt_heap *heap;
 	int i;
 
-	if (!(ubifs_chk_flags & UBIFS_CHK_GEN))
+	if (!dbg_is_chk_gen(c))
 		return 0;
 	if (random32() & 3)
 		return 0;