added localparameters in CSRs to control reg bw and mcycle and minstret

Created by: davideschiavone

This PR should be LEC equivalent. However, it adds 2 localparameters in the cs_register file

MHPMCOUNTER_WIDTH

is by default 64b. For small, NON COMPLIANT designs, one can set in its local version of the core the value 32.

In addition, when PULP_PERF_COUNTERS is set to 1 (default 0), small, non compliant designs can decide to not IMPLEMENT the mcycle and minstret performance counters