Replace lw/sw and various arithmetic instructions with macros so the
code can work on 64-bit kernels as well.

Cc: <stable@vger.kernel.org> # 3.16+
Reviewed-by: Paul Burton <paul.burton@imgtec.com>
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: stable@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/10591/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>