Recent versions of UEFI have moved local APIC timer initialization into
the early SEC phase which runs out of ROM, prior to self-relocating
into RAM. This results in a hypervisor exit.
Currently bhyve prevents instruction emulation from segments that aren't
marked as "sysmem" aka guest RAM, with the vm_gpa_hold() routine failing.
However, there is no reason for this restriction: the hypervisor already
controls whether EPT mappings are marked as executable.
Fix by dropping the redundant check of sysmem.
(Note: this problem was first seen by D Scott Phillips and worked around in
UEFI by moving APIC initialization to the later PEI phase