regulator: 88pm8607: Remove unused fields from struct pm8607_regulator_info

The *i2c and *i2c_8606 are no longer used since this driver was converted
to use regmap helpers. The *chip and *regulator are not really required.
So remove these unused fields.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Mark Brown <broonie@kernel.org>