xfs: remove the crc variable in __xfs_btree_check_lblock

crc is only used once, just use the xfs_has_crc check directly.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>