[media] si4713: move supply list to si4713_platform_data

The supply list is needed by the platform driver, but not by the usb driver.
So this information belongs to the platform data and should not be hardcoded
in the subdevice driver.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Tested-by: Eduardo Valentin <edubezval@gmail.com>
Acked-by: Eduardo Valentin <edubezval@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>