gpio: pl061: convert to use generic irq chip

Convert the pl061 irq_chip code to use the generic irq chip code.

This has the side effect of using 32-bit accesses rather than 8-bit
accesses to interrupt registers. The h/w TRM and testing seem to indicate
this is fine.

Signed-off-by: Rob Herring <rob.herring@calxeda.com>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 8482a23..4d433e2 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -138,6 +138,7 @@
 config GPIO_PL061
 	bool "PrimeCell PL061 GPIO support"
 	depends on ARM_AMBA
+	select GENERIC_IRQ_CHIP
 	help
 	  Say yes here to support the PrimeCell PL061 GPIO device