gpio: davinci: Add the missing of-node pointer

Currently the first parameter of irq_domain_add_legacy is NULL.
irq_find_host function returns NULL when we do not populate the of_node
and hence irq_of_parse_and_map call fails whenever we want to request a
gpio irq. This fixes the request_irq failures for gpio interrupts.

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>