regulator: rk808: remove linear range definitions with a single range

The driver was using only linear ranges. Now we remove linear range
definitions with a single range. So we have to add an ops struct for
ranges and adjust all other ops functions accordingly.

Signed-off-by: Wadim Egorov <w.egorov@phytec.de>
Signed-off-by: Mark Brown <broonie@kernel.org>