media: si470x-i2c: Add device tree support

This commit enables device tree support adding simple of_match table.

Signed-off-by: Pawe? Chmiel <pawel.mikolaj.chmiel@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>