tpm: apci: cleanup TCPA table initialization

tpm: apci: cleanup TCPA table initialization

At the time build_tpm_tcpa() is called the tcpalog size is
always 0, so log_area_start_address which is actually offset
from the start of ACPI_BUILD_TPMLOG_FILE is always 0.

Also as 'TCPA' is allocated 0 filled, there is no point
in calculating always 0 log_area_start_address and set
tcpa->log_area_start_address to it since the field should
always point to start of ACPI_BUILD_TPMLOG_FILE.
Make code easier to read dropping not needed offset
calculations.
While at that move tcpalog allocation closer to the code
that defines its size.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>