pwm: samsung: Change prototype of helpers to prepare further changes

This prepares the driver for further changes that will make it harder to
determine the pwm_chip from a given samsung_pwm_chip. To just not have
to do that, rework pwm_samsung_calc_tin() and pwm_samsung_parse_dt take
a pwm_chip. Also use the pwm_chip as driver data instead of the
samsung_pwm_chip.

Link: https://lore.kernel.org/r/33ea7d7fbf3be4a542ae8aafa213470c5831487e.1707900770.git.u.kleine-koenig@pengutronix.de


Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>