pinctrl: exynos: Consolidate irq domain callbacks

Adding a irq_chip field to the samsung_pin_bank struct helps in
consolidating the irq domain callbacks for external gpio and wakeup
interrupt controllers. The exynos_wkup_irqd_ops and exynos_gpio_irqd_ops
have now been merged into a single exynos_eint_irqd_ops.

Signed-off-by: Abhilash Kesavan <a.kesavan@samsung.com>
Reviewed-by: Thomas Abraham <thomas.ab@samsung.com>
Tested-by: Thomas Abraham <thomas.ab@samsung.com>
Acked-by: Tomasz Figa <tomasz.figa@gmail.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Tomasz Figa <tomasz.figa@gmail.com>