tpm_tis: restore IRQ vector in IO memory after failed probing

If the probing finishes without success, it will leave the value 15 in
the TPM_IRQ_VECTOR register. If the driver is unloaded and reloaded, it
will "think" that the hardware had been programmed with IRQ 15, and will
not probe again.

This patch restores the original value in the IO memory if no IRQ is
probed.

Signed-off-by: Martin Wilck <Martin.Wilck@ts.fujitsu.com>
Acked-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Acked-by: Peter Huewe <PeterHuewe@gmx.de>