pinctrl/nomadik: make independent of <mach/irqs.h>

Some leftovers in the driver were using NOMADIK_* macros to
translate the irq numbers to offsets, while the first base IRQ
was already being passed from platform data, and the function
setting the disable mask could just as well use the irqdomain.

Reviewed-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>