devel/gdb: kgdb: fixup aarch64 pcb/trapframe layout

[kevans]

Summary

base 1c1f31a5e5 and 2ecbbcc7cab altered the pcb and trapframe layouts in osreldate 1400084. This version of the patch is effectively extracted from work done by @jhb in CheriBSD's gdb fork, then ported forward to work with the gdb 13.x program_space_data equivalent. With this + D39951, I can again get a solid backtrace in recent main.

[jhb]

For ${REASONS} unless you want to fill out FSF paperwork I need to make sure I reproduce this over in my kgdb branch (I'm close to being able to upstream most of kgdb as I'm just waiting on FSF paperwork for a couple of folks now.

[kevans]

In D41684#950083, @jhb wrote:

For ${REASONS} unless you want to fill out FSF paperwork I need to make sure I reproduce this over in my kgdb branch (I'm close to being able to upstream most of kgdb as I'm just waiting on FSF paperwork for a couple of folks now.

I'm more than happy to fill out some paperwork if it'll save you time and energy here (especially since this version is easily proven as a derivative of work you already did once).

[jhb]

This is ok. I ended up with a few different tweaks in my kgdb-13 branch which will hopefully end up upstream eventually, but will definitely end up in the update to GDB 14.

[emaste]

Looks reasonable to me