vmm(4): dt(4) tracepoints for vm exit reporting previous exit.

vmm(4): dt(4) tracepoints for vm exit reporting previous exit.

On Intel/VMX, the tracepoint for vm exits was before extracting the
vm exit reason meaning we either reported stack garbage (on first
exit) or the prior exit reason. Move the tracepoint to after
extraction and refactor the logic to collect all exit info processing
in one place. (We were extracting the guest RFLAGS register state
before checking the exit info extraction success.)

On AMD/SVM, the tracepoint was always triggered even on unsuccessful
vm entry leading to garbage data. Tuck the tracepoint into the If
block and merge them.

ok mlarkin@