mfd: pm8018-core: use pm8xxx-regulator instead of pm8018-regulator

Change the pm8018-core driver so that it registers devices for
the pm8xxx-regulator driver instead of for the pm8018-regulator
driver.

This necessitates changing board file platform data for existing
PMIC 8018 regulators so that additional pm8xxx-regulator data is
properly specified.

Change-Id: I3f64f756a6c48c0dd1684f8d8e98a6fa8dddd6ca
Signed-off-by: David Collins <collinsd@codeaurora.org>