dt-bindings: media: camss: Add qcom,sdm670-camss

As found in the Pixel 3a, the Snapdragon 670 has a camera subsystem with
3 CSIDs and 3 VFEs (including 1 VFE lite). Add this camera subsystem to
the bindings.

Adapted from SC8280XP camera subsystem.

Signed-off-by: Richard Acayan <mailingradian@gmail.com>
Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>