ArmVirtPkg/PlatformPeiLib: discover the TPM base address from the DT

ArmVirtPkg/PlatformPeiLib: discover the TPM base address from the DT

Introduce a boolean PCD that tells us whether TPM support is enabled
in the build, and if it is, record the TPM base address in the existing
routine that traverses the device tree in the platform PEIM.

If a TPM is found, install the gOvmfTpmDiscoveredPpiGuid signalling PPI
that will unlock the dispatch of OvmfPkg's Tcg2ConfigPei. If TPM2
support is enabled in the build but no TPM2 device is found, install the
gPeiTpmInitializationDonePpiGuid PPI, which is normally installed by
Tcg2ConfigPei if no TPM2 is found, but in our case Tcg2ConfigPei will
never run so let's do it here instead.

Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=2560
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Laszlo Ersek <lersek@redhat.com>