tpm_tis: Introduce durations sysfs entry

Display the TPM's command timeouts in a 'durations' sysfs entry. Display
the entries as having been adjusted when they were scaled due to their values
being reported in milliseconds rather than microseconds.

Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
Tested-by: Guillaume Chazarain <guichaz@gmail.com>
Signed-off-by: Rajiv Andrade <srajiv@linux.vnet.ibm.com>