The BQ27510 and BQ27520 use a slightly different register map than the
BQ27500, add a new type enum and add these gauges to it.

Fixes: d74534c2 ("power: bq27xxx_battery: Add support for additional bq27xxx family devices")
Based-on-patch-by: Kenneth R. Crudup <kenny@panix.com>
Signed-off-by: Andrew F. Davis <afd@ti.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>