mfd: da9062: Remove IRQ requirement

This patch removes the requirement for an IRQ, because for the core
functionality IRQ isn't needed. So this makes the DA9061/62 chip
usable for designs which haven't connected the IRQ pin.

Signed-off-by: Christoph Niedermaier <cniedermaier@dh-electronics.com>
Acked-by: Adam Ward <DLG-Adam.Ward.opensource@dm.renesas.com>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20230309092254.56279-2-cniedermaier@dh-electronics.com