regulator: 88pm8607: fix indent code style

Fix indent code style in order to fix the following checkpatch
issues.

  ERROR: code indent should use tabs where possible
  WARNING: please, no space before tabs
  WARNING: please, no spaces at the start of a line
Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Acked-by: Haojian Zhuang <haojian.zhuang@gmail.com>
Signed-off-by: Mark Brown <broonie@linaro.org>