ARM: dt: tegra: seaboard: add regulators

ARM: dt: tegra: seaboard: add regulators

Seaboard uses a TPS6586x regulator. Instantiate this, and hook up a
couple of fixed GPIO-controlled regulators too.

Two data sources were used for the data encoded here:
* The HW defaults, as extracted from real HW.
* The schematic, which specifies a voltage for each LDO rail.

In most cases these sources matched. The only differences is:

ldo6: The HW default on Springbank is 2.85v. The HW default on Seaboard
is 1.8v. The schematics for both Springbank and Seaboard match at 2.85v.
However, internal research indicates that the schematics are incorrectly
labelled, and 1.8v is correct. The ChromeOS kernel also uses 1.8v.

Note that these settings don't entirely match those in the ChromeOS
kernel found at the URL below. However, the selected values generally
cause no behavior change in the kernel, and so were picked to avoid
regressions.

repo http://git.chromium.org/chromiumos/third_party/kernel.git
branch chromeos-3.2
file arch/arm/mach-tegra/board-seaboard-power.c

Portions based on work by Laxman Dewangan <ldewangan@nvidia.com>

Signed-off-by: Stephen Warren <swarren@nvidia.com>