just send data to lsroq to shorten load miss penalty.

* Exception for MiscUnit is not enabled because of issue queue problems

We do not block it, we nack it and let it go.

no need to send to dcache.

Originally, every request goes to DCache LoadPipe, even mmio ones.
And miss and mmio signals are passed down by DCache LoadPipe.
Now, mmio reqs don't go through DCache LoadPipe, their signals are
passed down by LoadUnit L2, L3 and L4 pipeline stages.

Passed all cputests.