power: qcom: Add QTI QBG(Qualcomm Battery Gauging) driver

Add support for Qualcomm Technologies, Inc. Battery Gauge driver
which uses periodic samples of the battery voltage and current to
determine the battery state-of-charge (SOC) and supports other
battery management features.

Change-Id: I6d342ef9c074ca5740a9091c305cfabd68143918
Signed-off-by: Shyam Kumar Thella <sthella@codeaurora.org>