UBIFS: separate debugging fields out

Introduce a new data structure which contains all debugging
stuff inside. This is cleaner than having debugging stuff
directly in 'c'.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
diff --git a/fs/ubifs/tnc_commit.c b/fs/ubifs/tnc_commit.c
index 8ac76b1..3c0af45 100644
--- a/fs/ubifs/tnc_commit.c
+++ b/fs/ubifs/tnc_commit.c
@@ -553,8 +553,8 @@
 	}
 
 #ifdef CONFIG_UBIFS_FS_DEBUG
-	c->new_ihead_lnum = lnum;
-	c->new_ihead_offs = buf_offs;
+	c->dbg->new_ihead_lnum = lnum;
+	c->dbg->new_ihead_offs = buf_offs;
 #endif
 
 	return 0;
@@ -1002,7 +1002,8 @@
 	}
 
 #ifdef CONFIG_UBIFS_FS_DEBUG
-	if (lnum != c->new_ihead_lnum || buf_offs != c->new_ihead_offs) {
+	if (lnum != c->dbg->new_ihead_lnum ||
+	    buf_offs != c->dbg->new_ihead_offs) {
 		ubifs_err("inconsistent ihead");
 		return -EINVAL;
 	}