OvmfPkg/AcpiPlatformDxe: remove the "AcpiPlatformDxe.inf" driver

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>
Message-Id: <20210526201446.12554-13-lersek@redhat.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Leif Lindholm <leif@nuviainc.com>