In 570a3609 IRQ path is incorrectly always exercised while it should be
exercised only when there is an IRQ number allocated. This commit
reverts the old behavior.

[jarkko.sakkinen@linux.intel.com: updated description]

Fixes: 570a3609 ("tpm: drop 'irq' from struct tpm_vendor_specific")
Signed-off-by: Andrew Zamansky <andrew.zamansky@nuvoton.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>