xfs: return a distinct error code value for IGET_INCORE cache misses

For an XFS_IGET_INCORE iget operation, if the inode isn't in the cache,
return ENODATA so that we don't confuse it with the pre-existing ENOENT
cases (inode is in cache, but freed).
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

fs/xfs/xfs_icache.c

@@ -610,7 +610,7 @@ xfs_iget(
 	} else {
 		rcu_read_unlock();
 		if (flags & XFS_IGET_INCORE) {
-			error = -ENOENT;
+			error = -ENODATA;
 			goto out_error_or_again;
 		}
 		XFS_STATS_INC(mp, xs_ig_missed);