xfs: remove a duplicate assignment in xfs_bmap_add_extent_delay_real

Reported-by: NBrian Foster <bfoster@redhat.com>
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NBrian Foster <bfoster@redhat.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

fs/xfs/libxfs/xfs_bmap.c

@@ -1765,7 +1765,7 @@ xfs_bmap_add_extent_delay_real(
 		LEFT.br_blockcount += new->br_blockcount;
 		xfs_iext_update_extent(bma->ip, state, bma->idx - 1, &LEFT);
 
-		PREV.br_blockcount = temp = PREV.br_blockcount - new->br_blockcount;
+		PREV.br_blockcount = temp;
 		PREV.br_startoff += new->br_blockcount;
 		PREV.br_startblock = nullstartblock(da_new);
 		xfs_iext_update_extent(bma->ip, state, bma->idx, &PREV);