power: bq25890: simplify chip name property getter

Driver rejects unknown chips early in the probe(), so when
bq25890_power_supply_get_property() is made reachable, bq->chip_version
will already be set to correct value - there is no need to check
it again.

Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>