Implement emulation of GINVT instruction. As QEMU doesn't support
caches and virtualization, this implementation covers only one
instruction (GINVT - Global Invalidate TLB) among all TLB-related
MIPS instructions.

Reviewed-by: Aleksandar Rikalo <aleksandar.rikalo@rt-rk.com>
Signed-off-by: Yongbok Kim <yongbok.kim@mips.com>
Signed-off-by: Aleksandar Markovic <amarkovic@wavecomp.com>
Message-Id: <1579883929-1517-5-git-send-email-aleksandar.markovic@rt-rk.com>