regulator: Revert coupled regulator support again

Revert the last two commits of the voltage coupling mechanism patch set:

456e7cdf regulator: core: Change voltage setting path
69686176 regulator: core: Add voltage balancing mechanism

as they broke boot on OMAP again.
Reported-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Mark Brown <broonie@kernel.org>