OvmfPkg/AcpiPlatformDxe: remove the "AcpiPlatformDxe.inf" driver
    
    The "OvmfPkg/AcpiPlatformDxe/AcpiPlatformDxe.inf" module is no longer
    referenced in any platform DSC file; remove it.
    
    That orphans the "AcpiPlatform.c", "Qemu.c" and "Xen.c" files in the
    "OvmfPkg/AcpiPlatformDxe/" directory; remove them.
    
    That in turn removes the only definitions of the InstallAcpiTable(),
    QemuDetected(), QemuInstallAcpiTable(), InstallXenTables() functions in
    the "OvmfPkg/AcpiPlatformDxe/" directory, so remove their declarations
    from "AcpiPlatform.h".
    
    Remove "OvmfPkg/AcpiPlatformDxe/Xen.c" from the "OvmfPkg: Xen-related
    modules" section of "Maintainers.txt", as well.
    
    Cc: Andrew Fish <afish@apple.com>
    Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
    Cc: Jordan Justen <jordan.l.justen@intel.com>
    Cc: Leif Lindholm <leif@nuviainc.com>
    Cc: Michael D Kinney <michael.d.kinney@intel.com>
    Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
    Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=2122
    Signed-off-by: Laszlo Ersek <lersek@redhat.com>