pwm: fsl-ftm: Prepare removing pwm_chip from driver data

This prepares the driver for further changes that will drop struct
pwm_chip chip from struct fsl_pwm_chip. Use the pwm_chip as driver data
instead of the fsl_pwm_chip to get access to the pwm_chip in
fsl_pwm_suspend() and fsl_pwm_resume() without using fpc->chip.

Link: https://lore.kernel.org/r/2cf27e2929505c05f84501d6fce96f23eba03fc3.1707900770.git.u.kleine-koenig@pengutronix.de


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