pwm: dwc: Add 16 channel support for Intel Elkhart Lake

Intel Elkhart Lake PSE includes two instances of PWM as a single PCI
function with 8 channels each. Add support for the remaining channels.

Signed-off-by: Raag Jadav <raag.jadav@intel.com>
Tested-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Tested-by: Lakshmi Sowjanya D <lakshmi.sowjanya.d@intel.com>
Link: https://lore.kernel.org/r/20240219033835.11369-4-raag.jadav@intel.com


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