staging: media: tegra-video: Fix -Wmaybe-unitialized warn in gcc

Make sure that tegra20_vi_get_input_formats always assign a value for
yuv_input_format.

Fix:
drivers/staging/media/tegra-video/tegra20.c:624:72: warning: ‘yuv_input_format’ may be used uninitialized [-Wmaybe-uninitialized]

Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
Reviewed-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>