Zihpm coverpoint issues

[jordancarlin]

There is a potential issue with the Zicntr coverpoints not being hit if Zihpm is not supported on the DUT. The most likely one to give us issues is if we are trying to read a counter when its counter enable bit is 1. This would be impossible if the counter does not exist.

This could happen even if Zihpm is supported because an implementation defined number of counters are allowed.

[jordancarlin]

Leaving open for further investigation, but if we can't find a solution this should be ok as is because it is just a coverage issue for implementations that don't implement all of the counters. The tests themselves will still work for any implementation.