riscv: Don't print zero offsets for register addresses

[jhb]

Summary

This matches the behavior of db_printsym.

Sponsored by: DARPA

[mhorne]

sys/riscv/riscv/trap.c

149–156

We can't call db_printsym() or some similar routine here?

[markj]

sys/riscv/riscv/trap.c

149–156

I'd assume that DDB functions with side effects are written assuming that they'll only ever run on a single CPU. print_with_symbol() is called right before a panic and so isn't serialized, so calling db_printsym() etc. here isn't quite right.

In practice it probably wouldn't hurt anything.

[jhb]

sys/riscv/riscv/trap.c

149–156

You'd be interleaving calls to db_printf with calls to regular printf within a single line which I think would not be ideal and probably confusing somewhere.