bindings: binding documentation for QPNP SMBLITE charger driver

The QPNP SMBLITE charger driver supports the charger peripherals present
in the PMIC PM2250. PM2250 incorporates a single input switch/linear mode
battery charger for single-cell Lithium batteries.

Register access is provided by the parent device via regmap. Interrupts
are controlled by the parent device, and handlers are registered by the
QPNP SMBLITE charger driver.

The power supply framework is used to communicate battery and usb
properties to userspace and other driver consumers such as fuel gauge,
USB.

Change-Id: Ie1b56902f474b326d6709cb841e06c36811ec76d