regulator: s2mps11: Convert driver completely to use set_ramp_delay callback

Since now we have ramp_delay and ramp_disable as standard regulator
constraints and DT part using it so this patch removes legacy part i.e. getting
ramp_delayxx and ramp_enable from pdata since it can be passed as
standard regulator constraints.

Signed-off-by: Yadwinder Singh Brar <yadi.brar@samsung.com>
Signed-off-by: Mark Brown <broonie@linaro.org>