mips32: Sync Caches to Make Instr Writes Effective

mips32: Sync Caches to Make Instr Writes Effective

Pprogram that loads another program into memory is actually writing the
D- side cache.
The instructions it has loaded can't be executed until they reach the
I-cache.

After the instructions have been written, the loader should arrange to
write back any containing D-cache line and invalidate any locations
already in the I-cache.

For the MIPS Architecture Release2 cores, we can use synci command
that does this job.
For Release1 we must use "cache" instruction.