bhyve.8: Remove mention of the -A flag

It is a no-op on amd64 now and is not implemented on arm64, so let's
remove mention of it altogether so as to reduce confusion for arm64
users.

Reviewed by: corvink, jhb
Sponsored by: Innovate UK
Differential Revision: https://reviews.freebsd.org/D44737

bhyve: Push option parsing down into bhyverun_machdep.c

After a couple of attempts I think this is the cleanest approach despite
the expense of some code duplication. Quite a few of the single-letter
bhyve options are x86-specific.

I think that going forward we should strongly discourage the addition of
new options and instead configure guests using the more general
configuration file syntax.

Reviewed by: corvink, jhb
MFC after: 2 weeks
Sponsored by: Innovate UK
Differential Revision: https://reviews.freebsd.org/D41753

bhyve: Replace many fprintf(stderr, ...) calls with EPRINTLN

EPRINTLN handles newlines appropriately when stdout/stderr have been
reused as the backend for a serial port.

For bhyverun.c itself, the rule this attempts to follow is to use
regular fprintf/perror/warn/err prior to init_pci() (which is when
serial ports are configured) and to switch to EPRINTLN afterwards.

Reviewed by: corvink, markj
Differential Revision: https://reviews.freebsd.org/D42182

bhyve: Move most early initialization into an MD routine

Prior to initializing PCI devices, main() calls a number of
initialization routines, many of which are amd64-specific. Move this
list of calls to bhyverun_machdep.c. Similarly, add an MD function to
handle late initialization.

No functional change intended.

Reviewed by: corvink, jhb
MFC after: 1 week
Sponsored by: Innovate UK
Differential Revision: https://reviews.freebsd.org/D40989

bhyve: Move vcpu initialization into a MD source file

- Make handling of x86 config options, like x86.x2apic, conditional to
amd64.
- Move fbsdrun_set_capabilities() and spinup_vcpu() to a new file,
bhyverun_machdep.c. The moved code is all highly x86 specific.

I'm not sure how best to handle the namespace. I'm using "bhyve_" for
MD functions called from MI code. We also have "fbsdrun_" for some MI
routines that are typically called from MD code. The file name is
prefixed by "bhyverun_".

Reviewed by: corvink
MFC after: 1 week
Sponsored by: Innovate UK
Differential Revision: https://reviews.freebsd.org/D40987