regulator: palma: add ramp delay support through regulator constraints

Currently Palma regulator driver support the ramp delay
through rail specific platform data.

As regulator framework support the configuration of ramp
delay through regulator constraint, using the framework
method and removing the platform specific data approach.

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Acked-by: Graeme Gregory <gg@slimlogic.co.uk>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>