acpi: Move build_tpm2() in the generic part

We plan to build the TPM2 table on ARM too. In order to reuse the
generation code, let's move build_tpm2() to aml-build.c.

No change in the implementation.

Signed-off-by: Eric Auger <eric.auger@redhat.com>
Message-Id: <20200601095737.32671-3-eric.auger@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>