regulator: Remove max_uV from struct regulator_linear_range

linear ranges means each range has linear voltage settings.
So we can calculate max_uV for each linear range in regulator core rather than
set the max_uV field in drivers.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Mark Brown <broonie@linaro.org>