pinctrl/coh901: use irqdomain, allocate irqdescs

This switches the COH 901 pinctrl driver to allocate its GPIO
IRQs dynamically, and start to use a linear irqdomain to map
from the hardware IRQs.

This way we can cut away the complex allocation of IRQ numbers
from the <mach/irqs.h> file.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

include/linux/platform_data/pinctrl-coh901.h

@@ -13,13 +13,11 @@
  * struct u300_gpio_platform - U300 GPIO platform data
  * @ports: number of GPIO block ports
  * @gpio_base: first GPIO number for this block (use a free range)
- * @gpio_irq_base: first GPIO IRQ number for this block (use a free range)
  * @pinctrl_device: pin control device to spawn as child
  */
 struct u300_gpio_platform {
 	u8 ports;
 	int gpio_base;
-	int gpio_irq_base;
 	struct platform_device *pinctrl_device;
 };