pwm: dwc: allow suspend/resume for 16 channels

With 16 channel pwm support, we're registering two instances of pwm_chip
with 8 channels each. We need to update PM functions to use both instances
of pwm_chip during power state transitions.

Introduce struct dwc_pwm_drvdata and use it as driver_data, which will
maintain both instances of pwm_chip along with dwc_pwm_info and allow us
to use them inside suspend/resume handles.

Fixes: ebf2c89e

 ("pwm: dwc: Add 16 channel support for Intel Elkhart Lake")
Signed-off-by: Raag Jadav <raag.jadav@intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20240415074051.14681-1-raag.jadav@intel.com
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>