regmap: regmap-irq/gpio-max77620: add level-irq support

Add level active IRQ support to regmap-irq irqchip. Change breaks
existing regmap-irq type setting. Convert the existing drivers which
use regmap-irq with trigger type setting (gpio-max77620) to work
with this new approach. So we do not magically support level-active
IRQs on gpio-max77620 - but add support to the regmap-irq for chips
which support them =)

We do not support distinguishing situation where HW supports rising
and falling edge detection but not both. Separating this would require
inventing yet another flags for IRQ types.

Signed-off-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
Signed-off-by: Mark Brown <broonie@kernel.org>