dm: regulator: uclass driver code cleanup

This cleanup includes:
- remove of the preprocessor macros which pointed to long name functions
- update of the names of some regulator uclass driver functions
- cleanup of the function regulator_autoset()
- reword of some comments of regulator uclass header file
- regulator_get_by_platname: check error for uclass_find_* function calls
- add function: regulator_name_is_unique
- regulator post_bind(): check regulator name uniqueness
- fix mistakes in: regulator/Kconfig
- regulator.h: update comments
- odroid u3: cleanup the regulator calls

Signed-off-by: Przemyslaw Marczak <p.marczak@samsung.com>
Acked-by: Simon Glass <sjg@chromium.org>
Tested on sandbox:
Tested-by: Simon Glass <sjg@chromium.org>