btrfs: Fix compilation with user namespace support enabled

When compiling with user namespace support btrfs fails like:

fs/btrfs/tree-log.c: In function ‘fill_inode_item’:
fs/btrfs/tree-log.c:2955:2: error: incompatible type for argument 3 of ‘btrfs_set_inode_uid’
fs/btrfs/ctree.h:2026:1: note: expected ‘u32’ but argument is of type ‘kuid_t’
fs/btrfs/tree-log.c:2956:2: error: incompatible type for argument 3 of ‘btrfs_set_inode_gid’
fs/btrfs/ctree.h:2027:1: note: expected ‘u32’ but argument is of type ‘kgid_t’

Fix this by using i_uid_read and i_gid_read in

Cc: Chris Mason <chris.mason@fusionio.com>
Cc: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

fs/btrfs/tree-log.c

@@ -2952,8 +2952,8 @@ static void fill_inode_item(struct btrfs_trans_handle *trans,
 			    struct btrfs_inode_item *item,
 			    struct inode *inode, int log_inode_only)
 {
-	btrfs_set_inode_uid(leaf, item, inode->i_uid);
-	btrfs_set_inode_gid(leaf, item, inode->i_gid);
+	btrfs_set_inode_uid(leaf, item, i_uid_read(inode));
+	btrfs_set_inode_gid(leaf, item, i_gid_read(inode));
 	btrfs_set_inode_mode(leaf, item, inode->i_mode);
 	btrfs_set_inode_nlink(leaf, item, inode->i_nlink);