[BUG] Incorrect instruction counting (MINSTRET) when executing a DRET in Machine mode.

Created by: LeeHoff

Bug Description

On the execution of dret when in machine mode, the DUT is incrementing minstret. As the dret causes an exception it is not retired and as such should not increment minstret. Found during simulation of the debug_test with step-and-compare.

Privileged Specification, 3.1.10 Hardware Performance Monitor: The minstret CSR counts the number of instructions the hart has retired