ISACOV : Fix #1425

Created by: AyoubJalali

Hello, So as we discus a log time about this issue, and we end up with the idea that we need a core-v-decoder, but isn't that easy for now, I made a fix related to the issue, Please have a look at it. Also I did a second commit to remove the rd filed from the coverage model, for c.jr & c.jalr as we discuss in the issue 1444