genirq: Introduce irq_chip_get/set_parent_state calls

On certain QTI chipsets some GPIOs are direct-connect interrupts
to the GIC.

Even when GPIOs are not used for interrupt generation and interrupt
line is disabled, it does not prevent interrupt to get pending at
GIC_ISPEND. When drivers call enable_irq unwanted interrupt occures.

Introduce irq_chip_get/set_parent_state calls to clear pending irq
which can get called within irq_enable of child irq chip to clear
any pending irq before enabling.

Change-Id: Ie8559657bd8da926cc741514809ffe9adbd73a80
Signed-off-by: Maulik Shah <mkshah@codeaurora.org>