pwm: Drop pwm_[sg]et_chip_data()

The semantic of chip_data is a bit surprising as it's cleared when
pwm_put() is called. Also there is a big overlap with the standard driver
data.

All drivers were adapted to not make use of chip_data any more, so it can
go away.

Link: https://lore.kernel.org/r/20230705080650.2353391-9-u.kleine-koenig@pengutronix.de
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>