regmap-irq: Fix typo in documentation for .get_irq_reg()

It refers to a non-existent "num_type_settings" value, which is
an old name I'd used during development of config registers and
later dropped because it wasn't very clear.

The correct bound for the range is num_config_regs, which can
be verified by checking the implementation.

Signed-off-by: Aidan MacDonald <aidanmacdonald.0x0@gmail.com>
Link: https://lore.kernel.org/r/20230509110100.3980123-2-aidanmacdonald.0x0@gmail.com


Signed-off-by: Mark Brown <broonie@kernel.org>