regulator: max8997: reorder buck1/2/5 dvs setup code

The BUCKxDVSx register programming is now moved prior to setting up of the
gpio based dvs mode. This will ensure that all the BUCKxDVSx registers
are programmed with appropriate voltage values before the gpio based dvs
mode is selected for buck1/2/5.

Signed-off-by: Thomas Abraham <thomas.abraham@linaro.org>
Reviewed-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>