Trying a quick access should give an unsupported response in ABS_CSR

**Type of issue**: bug report

**Impact**: unknown

**Development Phase**: proposal

**Other information**

**If the current behavior is a bug, please provide the steps to reproduce the problem:**
To reproduce, try a quick access command through the debug module.

**What is the current behavior?**
No action is performed and ABS_CSR reports 0, NO_ERROR, although the command is not (yet?) supported in the rocket chip.

**What is the expected behavior?**
I would expect ABS_CSR to report 2, UNSUPPORTED.

**Please tell us about your environment:**

**What is the use case for changing the behavior?**

Start in the debug module by tracing how a quick access command reaches ABS_CSR and how unsupported commands are reported. Reproduce the command described in the issue, then verify that the response changes from 0, NO_ERROR to 2, UNSUPPORTED.

Written by the indexing model from the issue text.