dquot: cleanup space allocation / freeing routines

Get rid of the alloc_space, free_space, reserve_space, claim_space and
release_rsv dquot operations - they are always called from the filesystem
and if a filesystem really needs their own (which none currently does)
it can just call into it's own routine directly.

Move shared logic into the common __dquot_alloc_space,
dquot_claim_space_nodirty and __dquot_free_space low-level methods,
and rationalize the wrappers around it to move as much as possible
code into the common block for CONFIG_QUOTA vs not.  Also rename
all these helpers to be named dquot_* instead of vfs_dq_*.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>

fs/ocfs2/quota_global.c

@@ -853,9 +853,7 @@ static void ocfs2_destroy_dquot(struct dquot *dquot)
 const struct dquot_operations ocfs2_quota_operations = {
 	.initialize	= dquot_initialize,
 	.drop		= dquot_drop,
-	.alloc_space	= dquot_alloc_space,
 	.alloc_inode	= dquot_alloc_inode,
-	.free_space	= dquot_free_space,
 	.free_inode	= dquot_free_inode,
 	.transfer	= dquot_transfer,
 	.write_dquot	= ocfs2_write_dquot,