msm: krait-regulator: add regulator control for kraits

Badger kraits have a single voltage supply coming from the pmic. This
supply is provided by multiple switching regulators operating in
ganged mode.

There is a LDO and a HS (Head Switch) per core that further control the
voltage supply to that core.

This driver manages the ganged supply by calling upon the spm driver to
set phases and voltage.

Change-Id: Idc0a0ae3242729a7e0ede5962974c09b61d8d39c
Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>