regulator: add QTI fixed voltage regulator driver

Add a new QTI fixed voltage regulator driver that is derived from
the fixed voltage regulator driver.  Use this to provide support
for proxy consumer voting and debug features required on Qualcomm
Technologies, Inc. boards.  Implement this driver as a wrapper
around fixed.c with #ifdef directives so that future updates to
fixed.c are applied automatically to qti-fixed-regulator.c.

Change-Id: If4cf664b3f6a8214256a4b2de753f7ff27aa864e
Signed-off-by: David Collins <collinsd@codeaurora.org>