regulator: lp872x: Remove **regulators from struct lp872x

Current code is using devm_regulator_register(), so we don't need to store *rdev
in struct lp872x for clean up.
Also clean up lp872x_probe() a bit to remove unnecessary goto and num_regulators
variable.

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