This patch adds support for the tps65090 charger driver. This driver is
responsible for controlling the charger aspect of the tps65090 mfd.
Currently, this mainly consists of turning on and off the charger, but
some features of the charger can be supported through this driver
including:

- Enable Auto Recharge based on Battery voltage
- Fast Charge Safety Timer
- Maximum battery discharge current
- Maximum battery adapter current
- Enable External Charge
- Disable charging termination based on low charger current (supported)

Once the driver is accepted, later patches can add support for the
features above which are not yet supported.

Based on work by:

  Syed Rafiuddin <srafiuddin@nvidia.com>
  Laxman Dewangan <ldewangan@nvidia.com>

Signed-off-by: Rhyland Klein <rklein@nvidia.com>
Signed-off-by: Anton Vorontsov <anton@enomsg.org>