regulator: pfuze100: Use i2c_[set|get]_clientdata

Since this is a i2c driver, use i2c_[set|get]_clientdata instead of
dev_[set|get]_drvdata.

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