drivers: parport: Ask user for irqreturn value

Current parport_irq_handler behaviour is not correct when IRQ is shared.
LDDv3 on page 279 requires us:

"Be sure to return IRQ_NONE whenever your handler is called and finds
the device is not interrupting."

This is not the case of parport_irq_handler.
Current implementation of IRQ handling use this to optimize shared IRQ processing.
When an action returns IRQ_HANDLED no other actions are processed.

Modify callback function void (*irq_func)(void *) to irqreturn_t (*irq_func)(void *) and return the value in parport_irq_handler

Signed-off-by: Matwey V. Kornilov <matwey@sai.msu.ru>