gpio: dwapb: Convert to use irqd_to_hwirq()

Convert to use irqd_to_hwirq() instead of direct access to the hwirq member.
Also amend the type of the hwirq holding variable to be irq_hw_number_t.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Tested-by: Serge Semin <fancer.lancer@gmail.com>
Reviewed-by: Serge Semin <fancer.lancer@gmail.com>
Cc: Serge Semin <fancer.lancer@gmail.com>
Link: https://lore.kernel.org/r/20200415141534.31240-7-andriy.shevchenko@linux.intel.com


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>