regulator: Merge tps65217_pmic_ldo234_ops and tps65217_pmic_dcdc_ops to tps65217_pmic_ops

Most callback functions implementation for tps65217_pmic_ldo234_ops and
tps65217_pmic_dcdc_ops are the same except the rid range checking.

This patch uses tps65217_pmic_ops for all DCDCx, LDO2, LDO3, and LDO4.
And rework tps65217_pmic_set_voltage to make it can be called for
DCDCx, LDO2, LDO3, and LDO4.

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>