regulator: enable compile testing for Maxim and Samsung PMIC drivers

Most of Maxim and Samsung PMIC/MUIC regulator drivers can be compile
tested to increase build coverage.  This allows to build them on
configurations without I2C (as I2C is required by dependency - parent
MFD driver).

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20200920214107.6299-1-krzk@kernel.org
Signed-off-by: Mark Brown <broonie@kernel.org>