OvmfPkg/QemuFlashFvbServicesRuntimeDxe: drop unused PCDs

OvmfPkg/QemuFlashFvbServicesRuntimeDxe: drop unused PCDs

The only two OvmfPkg references to "PcdFlashNvStorageVariableBase" are the
spurious ones in the runtime DXE driver and the SMM driver INF files of
the QEMU flash driver. Remove these references.

The flash driver does not access "PcdOvmfFlashNvStorageEventLogBase"
either, so remove that from the INF files too.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=386
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <20200310222739.26717-2-lersek@redhat.com>
Acked-by: Leif Lindholm <leif@nuviainc.com>