pwm: Move PUV3 PWM driver to PWM framework

This commit moves the driver to drivers/pwm and converts it to the new
PWM framework.

Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>
Tested-by: Qin Rui <qinrui@mprc.pku.edu.cn>
Acked-by: Guan Xuetao <gxt@mprc.pku.edu.cn>