dw_lower: Use a more efficient lowering for ir_bk_parity.
dw_lower: Use a more efficient lowering for ir_bk_parity.

Eor(Parity(hi), Parity(lo)) -> Parity(Eor(hi, lo)).

libfirm/libfirm,libfirm/libfirm,MatzeB/libfirm,MatzeB/libfirm,libfirm/libfirm,MatzeB/libfirm,MatzeB/libfirm,MatzeB/libfirm,MatzeB/libfirm,MatzeB/libfirm,libfirm/libfirm,libfirm/libfirm