gpio: set parent irq on chained handlers

If the IRQ from the parent is nested the IRQ may need to be
resent under certain conditions. Currently the chained IRQ
handler in gpiolib does not handle connecting nested IRQs
but it is conceptually correct to indicate the actual parent
IRQ.

Reported-by: Grygorii Strashko <grygorii.strashko@ti.com>
Reported-by: Lothar Waßmann <LW@karo-electronics.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>