dquot: cleanup dquot transfer routine

Get rid of the transfer dquot operation - it is now always called from
the filesystem and if a filesystem really needs it's own (which none
currently does) it can just call into it's own routine directly.

Rename the now static low-level dquot_transfer helper to __dquot_transfer
and vfs_dq_transfer to dquot_transfer to have a consistent namespace,
and make the new dquot_transfer return a normal negative errno value
which all callers expect.

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

fs/ext2/inode.c

diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
index 71b032c..3cfcfd9 100644
--- a/fs/ext2/inode.c
+++ b/fs/ext2/inode.c
@@ -1459,7 +1459,7 @@
 		return error;
 	if ((iattr->ia_valid & ATTR_UID && iattr->ia_uid != inode->i_uid) ||
 	    (iattr->ia_valid & ATTR_GID && iattr->ia_gid != inode->i_gid)) {
-		error = vfs_dq_transfer(inode, iattr) ? -EDQUOT : 0;
+		error = dquot_transfer(inode, iattr);
 		if (error)
 			return error;
 	}