media: dt-bindings: Add bindings for TDA1997X

Define the device tree bindings for the TDA1997X.

Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Sakari Ailus <sakari.ailus@iki.fi>
Signed-off-by: Tim Harvey <tharvey@gateworks.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
[hans.verkuil@cisco.com: make a proper commit message]
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>