amd64: Make EFI runtime faults look less like panics

EFI runtime faults may be mistaken for kernel panics, and do not
necessarily represent actual problems. Try to differentiate them some
more by printing "EFI runtime trap" rather than "Fatal trap".

PR: 291193
Reviewed by: kib
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D56309

(cherry picked from commit ddabf7f3ea4f0497dc5a5ffcbbb1d852ea77a4cd)