target/mips: Add emulation of MMI instruction PCPYH

Add emulation of MMI instruction PCPYH. The emulation is implemented
using TCG front end operations directly to achieve better performance.

Signed-off-by: Mateja Marjanovic <mateja.marjanovic@rt-rk.com>
Signed-off-by: Aleksandar Markovic <amarkovic@wavecomp.com>
Reviewed-by: Aleksandar Rikalo <arikalo@wavecomp.com>
Message-Id: <1551712405-2530-2-git-send-email-mateja.marjanovic@rt-rk.com>