ARM: tegra: tamonten: add the base board regulators

Currently the Tamonten DTS define a fixed regulator for the 5V supply.
However this regulator is in fact on the base board. Fix this by
properly defining the regulators found on the base boards.

Signed-off-by: Alban Bedel <alban.bedel@avionic-design.de>
Signed-off-by: Stephen Warren <swarren@nvidia.com>