regulator: add snapshot of cpr-regulator driver and documentation

This snapshot is taken from msm-3.18 branch as of:

'commit c0b3f609196f ("ARM: dts: msm: Remove GPU mempool for msm8909")'

CRs-Fixed: 2160311
Change-Id: I2cb5a52ca9628d80a145c493b9ab90f913840ff7
Signed-off-by: Tirupathi Reddy <tirupath@codeaurora.org>