dump_callstack() mixes up callstack for different cpus

[rakslice]

Since the callstack is fed from the static prev_pc, and there's only a single one for both cpus, if it happens that the previous mk_trace_cb() call was for the other cpu, then the wrong previous PC gets put into the callstack.

plexus_20_emu/emu.c

Line 850 in d75a83c

static unsigned int prev_pc=0;