bhyve/arm64 status

[Kamil Koczurek]

I'm trying to cross-compile bhyve for espressobin myself, but I've
come across some problems. `make buildworld`* throws the following
errors:

1. on branch bhyvearm64:
```
make[4]: make[4]: don't know how to make bhyvectl.1. Stop
```

2. on branch bhyvearm64_refactor:
```
In file included from
/root/bhyve/ehh/freebsd/usr.sbin/bhyve/mmio//devemu_irq.c:14:
/root/bhyve/ehh/freebsd/sys/dev/virtio/mmio/virtio_mmio.h:36:1: error:
type specifier missing, defaults to 'int'
[-Werror,-Wimplicit-int]
DECLARE_CLASS(vtmmio_driver);
^
/root/bhyve/ehh/freebsd/sys/dev/virtio/mmio/virtio_mmio.h:36:15:
error: a parameter list without types is only allowed in a function
definition
DECLARE_CLASS(vtmmio_driver);
              ^
/root/bhyve/ehh/freebsd/sys/dev/virtio/mmio/virtio_mmio.h:41:2: error:
unknown type name 'device_t'
        device_t                        dev;
        ^
/root/bhyve/ehh/freebsd/sys/dev/virtio/mmio/virtio_mmio.h:42:2: error:
unknown type name 'device_t'
        device_t                        platform;
        ^
/root/bhyve/ehh/freebsd/sys/dev/virtio/mmio/virtio_mmio.h:49:2: error:
unknown type name 'device_t'
        device_t                        vtmmio_child_dev;
        ^
/root/bhyve/ehh/freebsd/sys/dev/virtio/mmio/virtio_mmio.h:57:19:
error: a parameter list without types is only allowed in a function
definition
int vtmmio_attach(device_t);
                  ^
```

Both builds were done on freshly installed FreeBSD 13.0 / amd64. I can
supply full logs if anybody wants to take a look at them.

* Using supplied build scripts from bhyvearm64-utils gives the same results.