tpm_ibmvtpm: properly handle interrupted packet receptions

When the TPM response reception is interrupted in the wait_event_interruptable
call, the TPM is still busy processing the command and will only deliver the
response later. So we have to wait for an outstanding response before sending
a new request to avoid trying to put a 2nd request into the CRQ. Also reset
the res_len before sending a command so we will end up in that
wait_event_interruptable() waiting for the response rather than reading the
command packet as a response.

The easiest way to trigger the problem is to run the following

cd /sys/device/vio/71000004

while :; cat pcrs >/dev/null; done

And press Ctrl-C. This will then display an error

tpm_ibmvtpm 71000004: tpm_transmit: tpm_recv: error -4

followed by several other errors once interaction with the TPM resumes.

tpm_ibmvtpm 71000004: A TPM error (101) occurred attempting to determine the number of PCRS.

Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
Tested-by: Hon Ching(Vicky) Lo <honclo@linux.vnet.ibm.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Reviewed-by: Ashley Lai <ashley@ashleylai.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Acked-by: Peter Huewe <peterhuewe@gmx.de>