platform_data/emc2305: define platform data for EMC2305 driver

Introduce platform data structure for EM2305 driver to allow configuration
device PWMs and thermal zones by passing required platform data
to the driver. If no platform data is provided, the driver is supposed
to work with default settings.

Signed-off-by: Michael Shych <michaelsh@nvidia.com>
Reviewed-by: Vadim Pasternak <vadimp@nvidia.com>
Link: https://lore.kernel.org/r/20220810171552.56417-2-michaelsh@nvidia.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>