ARM: pxa: add regulator_has_full_constraints to spitz board file

Add regulator_has_full_constraints() call to spitz board file to let
regulator core know that we do not have any additional regulators left.
This lets it substitute unprovided regulators with dummy ones.

This fixes the following warnings that can be seen on spitz if
regulators are enabled:

ads7846 spi2.0: unable to get regulator: -517
spi spi2.0: Driver ads7846 requests probe deferral

Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Acked-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>