regulator: fixed: Revert support for ACPI interface

This reverts commit 13bed58ce874 (regulator: fixed: add support for ACPI
interface).

While there does appear to be a practical need to manage regulators on ACPI
systems, using ad-hoc properties to describe regulators to the kernel presents
a number of problems (especially should ACPI gain first class support for such
things), and there are ongoing discussions as to how to manage this.

Until there is a rough consensus, revert commit 13bed58ce8748d43, which hasn't
been in a released kernel yet as discussed in [1] and the surrounding thread.

[1] http://lkml.kernel.org/r/20170125184949.x2wkoo7kbaaajkjk@sirena.org.uk

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Liam Girdwood <lgirdwood@gmail.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Lu Baolu <baolu.lu@linux.intel.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Rafael J. Wysocki <rafael@kernel.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Mark Brown <broonie@kernel.org>