power: supply: bq25890: Only use pdata->regulator_init_data for vbus

bq25890_platform_data.regulator_init_data is intended to only provide
regulator init_data for the vbus regulator.

Remove this from the regulator_config before registering the vsys
regulator. Otherwise the regulator_register() call for vsys will fail
because it tries to register duplicate consumer_dev_name + supply
names from init_data->consumer_supplies[], leading to the entire
probe of the bq25890 driver failing:

[   32.017501] bq25890-charger i2c-bq25892_main: Failed to set supply vbus
[   32.017525] bq25890-charger i2c-bq25892_main: error -EBUSY: registering vsys regulator
[   32.124978] bq25890-charger: probe of i2c-bq25892_main failed with error -16

Fixes: 14a3d159 ("power: supply: bq25890: Add Vsys regulator")
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Marek Vasut <marex@denx.de>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>