regulator: Refactor to use one da9052_ldo_ops/da9052_dcdc_ops for all LDOs/DCDCs

In current implementation, da9052_ldo_ops and da9052_ldo5_6_ops are very
similar, only the set_voltage is slightly different.
da9052_buckperi_ops and da9052_dcdc_ops are also similar.

This patch adds da9052_regulator_set_voltage for the set_voltage callback
used by all LDOs and DCDCs. Rework da9052_get_regulator_voltage_sel and
da9052_set_dcdc_voltage to make it possible to be shared by all DCDCs.
Rework da9052_list_voltage to make it to be shared by all DCDCs and LDOs.

Then we can remove da9052_ldo5_6_ops and da9052_buckperi_ops.
We can also remove DA9052_LDO5_6 and DA9052_BUCKPERI macros which is not used
now.
Signed-off-by: Axel Lin <axel.lin@gmail.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>