Ext2: return ENOMEM rather than EIO if sb_getblk fails

As the only reason that sb_getblks fails is that allocation fails.
It will be better to use ENOMEM rather than EIO.

Signed-off-by: Wang Shilong <[e-mail]>
Signed-off-by: Jan Kara <[e-mail]>

fs/ext2/xattr.c

···
 			if (unlikely(!new_bh)) {
 				ext2_free_blocks(inode, block, 1);
 				mark_inode_dirty(inode);
-				error = -EIO;
+				error = -ENOMEM;
 				goto cleanup;
 			}
 			lock_buffer(new_bh);