Kernel selftests: Add check if TPM devices are supported

TPM2 tests set uses /dev/tpm0 and /dev/tpmrm0 without check if they
are available. In case, when these devices are not available test
fails, but expected behaviour is skipped test.

Signed-off-by: Nikita Sobolev <Nikita.Sobolev@synopsys.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Reviewed-by: Petr Vorel <petr.vorel@gmail.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>