bq20z75: Rename to sbs-battery

This driver for the bq20z75 implemented the register spec defined
by the SBS standard. As this is not unique to this the TI part this
was originally written for, we can generalize this driver to
show its support for any SBS compliant battery.

Signed-off-by: Rhyland Klein <rklein@nvidia.com>
Signed-off-by: Anton Vorontsov <cbouatmailru@gmail.com>