PoR value of MSTATUS

Bug Description

The documented power-on-reset value of the mstatus CSR (0x300) is 0x0000_1800 which expands to:

Bit Pos	PoR	Field
21	1'b0	TW
17	1'b0	MPRV
12:11	2'b11	MPP
7	1'b0	MPIE
3	1'b0	MIE

However the coded PoR in the RTL is:

localparam status_t MSTATUS_RST_VAL = '{mie:  1'b0,
                                          mpie: 1'b1,
                                          mpp:  PRIV_LVL_U,
                                          mprv: 1'b0,
                                          tw:   1'b0};

Given that PRIV_LVL_U is 2'b00, this yields a PoR of 0x0000_0080.

I believe that the documented PoR value is the proper one, but the coded PoR has been in the Ibex code for three years so I am not certain.

You can show this in simulation in CORE-V-VERIF by running the debug_test:

$ make test TEST=debug_test

(Set the SIMULATOR and USE_ISS vars as appropriate for your installation.)