regmap: add regmap_might_sleep()

With the dawn of MMIO gpio-regmap users, it is desirable to let
gpio-regmap ask the regmap if it might sleep during an access so
it can pass that information to gpiochip. Add a new regmap_might_sleep()
to query the regmap.

Signed-off-by: Michael Walle <michael@walle.cc>
Link: https://lore.kernel.org/r/20221121150843.1562603-1-michael@walle.cc


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