regulator: s2mpa01: Optimize the regulator description macro

This patch makes the regulator description macro take minimum and
steps voltage as parameter. In this way many repeated macros can be
removed. Now these macros are repeated only if the the LDO/BUCK ctrl
registers have non-linear positions. The good thing is these ctrl registers
are mostly linear so they are not passed as parameters.

This patch reduces the code size and also allow easy addition of more
s2mpxxx PMIC drivers which differs a lot in minimum/step voltages.

Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Amit Daniel Kachhap <amit.daniel@samsung.com>
Signed-off-by: Mark Brown <broonie@linaro.org>