input: ti_am335x_tsc: ACK the HW_PEN irq in ISR

The interrupt source IRQENB_HW_PEN is enabled in suspend and suposed to
be used as a wake up source. Once this interrupt source is unmaksed, the
devices ends up in ISR and never continues.
This change ACKs the interrupt and disables it so the system does not
freeze.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>