pinctrl: qcom: spmi-gpio: fix warning about irq chip reusage

Fix the following warnings caused by reusage of the same irq_chip
instance for all spmi-gpio gpio_irq_chip instances. Instead embed
irq_chip into pmic_gpio_state struct.

gpio gpiochip2: (c440000.qcom,spmi:pmic@2:gpio@c000): detected irqchip that is shared with multiple gpiochips: please fix the driver.
gpio gpiochip3: (c440000.qcom,spmi:pmic@4:gpio@c000): detected irqchip that is shared with multiple gpiochips: please fix the driver.
gpio gpiochip4: (c440000.qcom,spmi:pmic@a:gpio@c000): detected irqchip that is shared with multiple gpiochips: please fix the driver.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>