Fixed performance counters to properly register the second commit port

Created by: OttG

Fixed perf_counters.sv to properly register the second commit port.

Fixed the checks for Calls and Returns. For Calls we check for both jal and jalr and wether the linking register is x1 (RA) or x5 (the alternative for the return address). For what is concerced Returns, fixed the check on rd to be 'd0 instead of 'd1. I tested these changes on matmult-int test from embench where on the current version it registers 1/10 of the actual branches (they most commit on port 2).

I added the possibility for increasing the counters by more than one per cycle (up to NR_COMMIT_PORTS), although this makes it a bit cluttery. Also, this might be very rare, maybe with store and loads it should be possible to commit 2 at a time but I'm not sure about branch/calls/returns. If you think is too messy I could revert that part as it was before.

Signed-off-by: Gianmarco Ottavi gianmarco@openhwgroup.org