arm64: dts: qcom: sdm845-db845c: Add ov8856 & ov7251 camera nodes

Enable the ov8856 main camera and the ov7251 b/w tracking camera
used on the Qualcomm RB3 kit.

Currently the camera nodes have not yet been attached to an to a
CSI2 endpoint, since no driver currently supports the ISP that the the
SDM845/db845c ships with.

Signed-off-by: Robert Foss <robert.foss@linaro.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20200324155843.10719-6-robert.foss@linaro.org
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>