pwm: clk: Prepare removing pwm_chip from driver data

This prepares the driver for further changes that will drop struct
pwm_chip chip from struct pwm_clk_chip. Use the pwm_chip as driver data
instead of the pwm_clk_chip to get access to the pwm_chip in
pwm_clk_remove() without using pcchip->chip.

Link: https://lore.kernel.org/r/cfbb7c571489ac3d9ca13835b3bd038aaca69638.1707900770.git.u.kleine-koenig@pengutronix.de


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