power: qpnp-charger: add qpnp charger driver

Add the qpnp charger driver which supports the
switch mode battery charger and boost (SMBB) on
Qualcomm PMIC chips.

This driver provides the following verified features:

 * PMIC USB detection
 * end of charging analog detection schema
 * userspace reporting:
 ** battery:
 *** temperature, voltage, status
 ** USB:
 *** online, presence and maximum current

Change-Id: I58acdbacb0cea2b69474c771e2b8b1d5b4a7becc
Signed-off-by: David Keitel <dkeitel@codeaurora.org>