[ARM] SMDK6410: Mark all supplies as always_on

Since no consumers are currently configured for the SMDK6410 mark all
the supplies on the board as being always_on, ensuring interoperability
with future regulator API changes to disable unused regulators.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>