The PRV field of DCSR is updated wrongly

Created by: shetalani

Apparently, executing dret to return from debug mode, that the hart has entered due to ebreak instruction with forced entry, brings the hart to M mode instead of U mode.

As in the following counter example, the whole dcsr is not updated for an ebreak instruction with a forced entry into debug mode (ebreaku is set in dcsr), thus, dret ends up moving the hart back wrongly to M mode.

Same case happens when debug mode is entered due to a debug request while the hart is operating in U mode.

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Product: OneSpin 360 DV-Verify App: RVV Tool's version: 2019.2.1