OvmfPkg/Bhyve: add support for QemuFwCfg

OvmfPkg/Bhyve: add support for QemuFwCfg

QemuFwCfg is much more powerful than BhyveFwCtl. Sadly, BhyveFwCtl
decided to use the same IO ports as QemuFwCfg. It's not possible to use
both interfaces simultaneously. So, prefer QemuFwCfg over BhyveFwCtl.

Signed-off-by: Corvin Köhne <c.koehne@beckhoff.com>
Reviewed-by: Rebecca Cran <rebecca@bsdio.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Peter Grehan <grehan@freebsd.org>
Acked-by: Jiewen Yao <jiewen.yao@intel.com>