pwm: Use device_get_match_data()

Use preferred device_get_match_data() instead of of_match_device() to
get the driver match data. With this, adjust the includes to explicitly
include the correct headers.

As these drivers only do DT based matching, of_match_device() will never
return NULL if we've gotten to probe(). Therefore, the NULL check and
error returns can be dropped.

Signed-off-by: Rob Herring <robh@kernel.org>
Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>