tpm_spapr: Support TPM for ppc64 using CRQ based interface

tpm_spapr: Support TPM for ppc64 using CRQ based interface

Implement support for TPM on ppc64 by implementing the vTPM CRQ interface
as a frontend. It can use the tpm_emulator driver backend with the external
swtpm.

The Linux vTPM driver for ppc64 works with this emulation.

This TPM emulator also handles the TPM 2 case.

Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Message-Id: <20200121152935.649898-4-stefanb@linux.ibm.com>
[dwg: Use device_class_set_props(), tweak Kconfig]
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>