pwm: sprd: Add Spreadtrum PWM support

This patch adds the Spreadtrum PWM support, which provides maximum 4
channels.

Signed-off-by: Neo Hou <neo.hou@unisoc.com>
Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
3 files changed