dt-bindings: regulator: document max77838 pmic

dt-bindings: regulator: document max77838 pmic

The max77838 is a pmic, containing a BUCK regulator and 4 LDOs. It's
primarily used in the Samsung Galaxy S7 lineup and is accessed over I2C.
Document it.

Signed-off-by: Ivaylo Ivanov <ivo.ivanov.ivanov1@gmail.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Igor Belwon <igor.belwon@mentallysanemainliners.org>
Link: https://patch.msgid.link/20250914130230.2622030-2-ivo.ivanov.ivanov1@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>