sys/v4l2/gstv4l2: fix the depth value for RGB32
sys/v4l2/gstv4l2: fix the depth value for RGB32

The 'depth' value for RGB32 must be 24 rather than 32.
This changes conversion code between color format
representaion in caps and V4L2 definition.

matsu/gst-plugins-good,matsu/gst-plugins-good,matsu/gst-plugins-good,matsu/gst-plugins-good