power: supply: bq2515x: fix kerneldoc

Fix kerneldoc W=1 warning:

  drivers/power/supply/bq2515x_charger.c:189: warning:
    Function parameter or member 'init_data' not described in 'bq2515x_device'

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>