regulator: tps65090: Register all regulators in single probe call

MFD driver registers the regulator driver once per device and
hence it is require to register all regulators in single probe
call.
Following are details of changes done to achieve this:
- Move the regulator enums to mfd header and remove the
  tps65090-regulator.h as it does not contain more info.
- Add max regulator and register all regulators even if there
  is no regulator init data from platform.
- Convert regulator init data to pointer type in platform data.
- Add input supply name in regulator desc to provide input supply.
- Separate desc information from driver information.
- Disable external control bit to have control through register write.

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>