power: qpnp-linear-charger: Add battery charging functionality

Linear charger supports battery charging via USB. Add the following
features to this charger driver
- Charger configuration
- Battery insertion/removal detection
- Charging, end-of-charge and recharge functionality
- Handling of exceptions such as battery temperature,
  insertion/removal of charger, charging failure etc.

Change-Id: Ifb4696a2b4c4c3b5edef5547e7abbd5d97151f50
Signed-off-by: Ashay Jaiswal <ashayj@codeaurora.org>