pinctrl: sirf: convert to linear irq domain

The sirf platforms use no hardcoded IRQ numbers, so there is no reason to
use the legacy domain, and by converting to the linear domain, we get
a more efficient representation of sparse IRQs and remove the dependency
on the mach/irqs.h header file.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Linus Walleij <linus.walleij@linaro.org>