tpm_tis: missing platform_driver_unregister() on error in init_tis()

Add the missing platform_driver_unregister() before return
from init_tis() in the device register error handling case.

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Kent Yoder <key@linux.vnet.ibm.com>