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>
diff --git a/drivers/regulator/Kconfig b/drivers/regulator/Kconfig
index ee1b322..1bd67e6 100644
--- a/drivers/regulator/Kconfig
+++ b/drivers/regulator/Kconfig
@@ -888,6 +888,16 @@
 	  This driver provides support for the voltage regulators on the
 	  WM8994 CODEC.
 
+config REGULATOR_CPR
+	bool "RBCPR regulator driver for APC"
+	depends on OF
+	help
+	  Compile in RBCPR (RapidBridge Core Power Reduction) driver to support
+	  corner vote for APC power rail. The driver takes PTE process voltage
+	  suggestions in efuse as initial settings. It converts corner vote
+	  to voltage value before writing to a voltage regulator API, such as
+	  that provided by spm-regulator driver.
+
 config REGULATOR_CPR3
 	bool "CPR3 regulator core support"
 	help