linux-imx

regulator: Add soft start support

Some regulators support a "soft start" feature where the voltage
ramps up slowly when the regulator is enabled. Add an op
(set_soft_start) and a DT property + constraint to support this.

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Mark Brown <broonie@kernel.org>