ext4: use ext4_reserve_inode_write in ext4_xattr_set_handle

ext4_mark_iloc_dirty() says:

 * The caller must have previously called ext4_reserve_inode_write().
 * Give this, we know that the caller already has write access to iloc->bh.

ext4_xattr_set_handle, however, just open-codes it.  May as well use
the helper function for consistency.

No bug here, just tidiness.

(Note: on cleanup path, ext4_reserve_inode_write sets
the bh to NULL if it returns an error, and brelse() of 
a null bh is handled gracefully).
Signed-off-by: NEric Sandeen <sandeen@redhat.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

fs/ext4/xattr.c

@@ -985,11 +985,7 @@ ext4_xattr_set_handle(handle_t *handle, struct inode *inode, int name_index,
 	no_expand = ext4_test_inode_state(inode, EXT4_STATE_NO_EXPAND);
 	ext4_set_inode_state(inode, EXT4_STATE_NO_EXPAND);
 
-	error = ext4_get_inode_loc(inode, &is.iloc);
-	if (error)
-		goto cleanup;
-
-	error = ext4_journal_get_write_access(handle, is.iloc.bh);
+	error = ext4_reserve_inode_write(handle, inode, &is.iloc);
 	if (error)
 		goto cleanup;