regulator: Refactor tps6507x to use one tps6507x_pmic_ops for all LDO…

…s and DCDCs

All the callback functions implementation for DCDCx and LDOx are very similar,
I think it is ok to use one tps6507x_pmic_ops for all LDOs and DCDCs.
This refactor removes a couple of duplicated code.

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