pwm: tegra: Add support to configure pin state in suspends/resume

In some of NVIDIA Tegra's platform, PWM controller is used to
control the PWM controlled regulators. PWM signal is connected to
the VID pin of the regulator where duty cycle of PWM signal decide
the voltage level of the regulator output.

When system enters suspend, some PWM client/slave regulator devices
require the PWM output to be tristated.

Add support to configure the pin state via pinctrl frameworks in
suspend and active state of the system.

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Acked-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>