UBIFS: introduce a separate structure for budgeting info

This patch separates out all the budgeting-related information
from 'struct ubifs_info' to 'struct ubifs_budg_info'. This way the
code looks a bit cleaner. However, the main driver for this is
that we want to save budgeting information and print it later,
so a separate data structure for this is helpful.

This patch is a preparation for the further debugging output
improvements.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
diff --git a/fs/ubifs/commit.c b/fs/ubifs/commit.c
index 1bd01de..87cd0ea 100644
--- a/fs/ubifs/commit.c
+++ b/fs/ubifs/commit.c
@@ -182,7 +182,7 @@
 	c->mst_node->root_len    = cpu_to_le32(zroot.len);
 	c->mst_node->ihead_lnum  = cpu_to_le32(c->ihead_lnum);
 	c->mst_node->ihead_offs  = cpu_to_le32(c->ihead_offs);
-	c->mst_node->index_size  = cpu_to_le64(c->old_idx_sz);
+	c->mst_node->index_size  = cpu_to_le64(c->bi.old_idx_sz);
 	c->mst_node->lpt_lnum    = cpu_to_le32(c->lpt_lnum);
 	c->mst_node->lpt_offs    = cpu_to_le32(c->lpt_offs);
 	c->mst_node->nhead_lnum  = cpu_to_le32(c->nhead_lnum);