OvmfPkg/Bhyve: make "PcdPciDisableBusEnumeration" Fixed-at-Build

OvmfPkg/Bhyve: make "PcdPciDisableBusEnumeration" Fixed-at-Build

The Bhyve platform specifies the dynamic access method for
"PcdPciDisableBusEnumeration" needlessly.

After the DSC file sets the PCD to TRUE by default, the PCD is never
written again. In particular, the
"OvmfPkg/Bhyve/PlatformPei/PlatformPei.inf" file references the PCD
superfluously.

Make the PCD Fixed-At-Build, and remove the PCD reference from the INF
file.

(Note that further simplifications are possible in
"OvmfPkg/Bhyve/AcpiPlatformDxe", but those are out of scope for this patch
series.)

Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Peter Grehan <grehan@freebsd.org>
Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
Cc: Rebecca Cran <rebecca@bsdio.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=2122
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <20210526201446.12554-25-lersek@redhat.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Rebecca Cran <rebecca@bsdio.com>