regmap-irq: Refactor checks for status bulk read support

There are several conditions that must be satisfied to support
bulk read of status registers. Move the check into a function
to avoid duplicating it in two places.

Signed-off-by: Aidan MacDonald <aidanmacdonald.0x0@gmail.com>
Link: https://lore.kernel.org/r/20220623211420.918875-8-aidanmacdonald.0x0@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>