tpm: use tpm_try_get_ops() in tpm-sysfs.c.

Use tpm_try_get_ops() in tpm-sysfs.c so that we can consider moving
other decorations (locking, localities, power management for example)
inside it. This direction can be of course taken only after other call
sites for tpm_transmit() have been treated in the same way.

Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
Tested-by: Stefan Berger <stefanb@linux.ibm.com>
Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Reviewed-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Tested-by: Alexander Steffen <Alexander.Steffen@infineon.com>