tpm: use tpm_transmit_cmd() in tpm2_probe()

It is better to tpm_transmit_cmd() in tpm2_probe() in order to get
consistent command handling throughout the subsystem.

Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Reviewed-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>