regulator: tps62360: Provide settling time for voltage change

Settling time is require when there is voltage output change.
Implement set_voltage_time_sel() callback which returns delay time
for voltage change to settle down to new value.

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>