bq20z75: Devicetree init support

Adding support to generate platform data when kernel is configured
through device tree.

Also adding the binding for the TI bq20z75 fuel gadge and the
bq20z75 driver.

Signed-off-by: Rhyland Klein <rklein@nvidia.com>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Anton Vorontsov <cbouatmailru@gmail.com>