regulator: core: Add PRE_DISABLE notification

Add a PRE_DISABLE notification so that consumers can use a
notifier to run any steps required to prepare for the
regulator being switched off. Since the regulator disable
can fail an abort notification is also added.

Change-Id: Ib7f77d27b3ba3ef2a7704247398db8ab6b625c42
Signed-off-by: Richard Fitzgerald <rf@opensource.wolfsonmicro.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Git-commit: a1c8a5512b7cddc81767172f0de37b155cea039f
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git


[osvaldob@codeaurora.org: resolve trivial merge conflicts]
Signed-off-by: Osvaldo Banuelos <osvaldob@codeaurora.org>