regulator: core: if voltage scaling fails, restore original voltage values

Change-Id: I6f41096966aa5e5f9d834049ca9b2ae2d8156285
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>
Tested-by: Robert Nelson <robertcnelson@gmail.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Git-commit: 92d7a55879c01b30349045501108e775655a4b92
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
[keliu@codeaurora.org: resolve merge conflicts]
Signed-off-by: Ke Liu <keliu@codeaurora.org>

Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>