OvmfPkg/AcpiPlatformDxe: clean up libs and protos in "AcpiPlatformDxe.inf"

None of the source files referenced by "AcpiPlatformDxe.inf" #include
"MdePkg/Include/Library/DxeServicesLib.h" or use interfaces declared
therein, so drop DxeServicesLib from [LibraryClasses].

"AcpiPlatformDxe.inf" references "AcpiPlatform.c", which installs ACPI
tables built into the firmware image from under "OvmfPkg/AcpiTables/", in
case dynamically generated ACPI tables are not available from Xen or QEMU.
For this, the driver consumes gEfiFirmwareVolume2ProtocolGuid. Account for
that in [Protocols].

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Steven Shi <steven.shi@intel.com>
Reported-by: Steven Shi <steven.shi@intel.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=1014
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>