staging: media: tegra-video: move tegra210_csi_soc to C file

This declaration is used only in csi.c, no need to export it elsewhere.

Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Reviewed-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>