[rv_dm] havereset may assert at incorrect time

[a-will]

Description

It appears havereset asserts when an NDM reset begins:

opentitan/hw/vendor/pulp_riscv_dbg/src/dm_csrs.sv

Lines 514 to 517 in 1fd378c

	// set the havereset flag when we did a ndmreset
	if (ndmreset_o) begin
	havereset_d_aligned[NrHarts-1:0] = '1;
	end

This does not follow spec. havereset should only assert once the reset completes, and it may be used as a synchronization point for the debugger. It's not used in openocd upstream yet (where there is a bug with merely checking allunavail), but it is properly checked in riscv-openocd.

[a-will]

CC @msfschaffner @andreaskurth

[msfschaffner]

CC @GregAC

[a-will]

Oh, this is a duplicate, it turns out.

Same issue as the following:
#15123
pulp-platform/riscv-dbg#118