pinctrl: armada-37xx: Fix irq mask access in armada_37xx_irq_set_type()

As explained in the following commit a9a1a483 ("pinctrl:
armada-37xx: Fix gpio interrupt setup") the armada_37xx_irq_set_type()
function can be called before the initialization of the mask field.

That means that we can't use this field in this function and need to
workaround it using hwirq.

Fixes: 30ac0d3b

 ("pinctrl: armada-37xx: Add edge both type gpio irq support")
Cc: stable@vger.kernel.org
Reported-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>
Link: https://lore.kernel.org/r/20191115155752.2562-1-gregory.clement@bootlin.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>