Move ia64 efi.h to sys in preparation for amd64 UEFI support

Prototypes specific to ia64 have been left in this file for now, under
__ia64__, rather than moving them to a new header under sys/ia64.
I anticipate that (some of) the corresponding functions will be shared
by the amd64, arm64, i386, and ia64 architectures, and we can adjust
this as EFI support on other than ia64 continues to develop.

Sponsored by:	The FreeBSD Foundation
Revert r263321.
vt(9) crash on resume fixed, but Xorg still have damaged screen on resume (at
least with i915kms), so better to switch to VT0 before suspend and back on
resume.

Sponsored by:	The FreeBSD Foundation