MIPS: Add MFHC0 and MTHC0 instructions to uasm.

New instructions for Extended Physical Addressing (XPA) functionality.

Signed-off-by: Steven J. Hill <Steven.Hill@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/8453/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>