amd64: on any fault during call to EFI RT, restore execution and print fault details
The fault info should be useful to see what specifically BIOS tried to
do and why it faulted. E.g. it might allow to see which EFI memory
segment needs to be mapped in addition to normal runtime segments, to
work around the fault.
Reviewed by: kevans, markj
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D48186