xfs: fix xfs_bmap_validate_extent_raw when checking attr fork of rt files

The realtime flag only applies to the data fork, so don't use the
realtime block number checks on the attr fork of a realtime file.

Fixes: 30b0984d91 ("xfs: refactor bmap record validation")
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>

fs/xfs/libxfs/xfs_bmap.c

@@ -6226,7 +6226,7 @@ xfs_bmap_validate_extent(
 
 	isrt = XFS_IS_REALTIME_INODE(ip);
 	endfsb = irec->br_startblock + irec->br_blockcount - 1;
-	if (isrt) {
+	if (isrt && whichfork == XFS_DATA_FORK) {
 		if (!xfs_verify_rtbno(mp, irec->br_startblock))
 			return __this_address;
 		if (!xfs_verify_rtbno(mp, endfsb))