This patch add the support of PWM controller which can be found at aspeed
ast2600 soc. The pwm supoorts up to 16 channels and it's part function
of multi-function device "pwm-tach controller".
Signed-off-by: Billy Tsai <billy_tsai@aspeedtech.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Chia-Wei Wang <chiawei_wang@aspeedtech.com>
