gpio: davinci: Do not assume continuous IRQ numbering

Currently the driver assumes that the interrupts are continuous
and does platform_get_irq only once and assumes the rest are continuous,
instead call platform_get_irq for all the interrupts and store them
in an array for later use.

Signed-off-by: Keerthy <j-keerthy@ti.com>
Reviewed-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>