tpm_tis_core: Set TPM_CHIP_FLAG_IRQ before probing for interrupts

The tpm_tis_core has to set the TPM_CHIP_FLAG_IRQ before probing for
interrupts since there is no other place in the code that would set
it.

Cc: linux-stable@vger.kernel.org
Fixes: 570a3609

 ("tpm: drop 'irq' from struct tpm_vendor_specific")
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>