ARM: dt: tegra: whistler: add regulators

ARM: dt: tegra: whistler: add regulators

Whistler uses a Maxim 8907 regulator. Instantiate this.

The voltage settings were derived from the schematic. The only exception
is the BBAT voltage; the schematic says 1.2v, but the HW can't go that
low, so use the HW default of 2.4v instead.

Almost all regulators list all driven supply signal names in their
regulator-names property. The exception is nvvdd_sv3, which is in turn
named 12 more different names on the schematic, so these were omitted
for brevity.

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