ARM: u300: support regulators in the device tree

Now that we have enabled board power and the AB3100 regulators,
put the regulator data into the device tree and enable it so
we can start to tie regulators to devices. To begin with we're
only supplying the power to the board itself.

Cc: Mark Brown <broonie@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>