OvmfPkg/QemuVideoDxe: enable ARM builds

The only feature not portable to ArmVirtualizationQemu is the VBE shim;
make that dependent on Ia32 / X64.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Acked-by: Olivier Martin <Olivier.martin@arm.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@16890 6f19259b-4bc3-4df7-8a09-765794883524