ipu: videotransform: use passthrough if caps are identical

Signed-off-by: Carlos Rafael Giani <dv@pseudoterminal.org>
ipu: videotransform: added fixate caps functions from videoconvert/scale

fixate caps code from gst-plugins-base videoconvert & videoscale merged
and put in use here, since videotransform can do both (scaling and
color space conversion)

Signed-off-by: Carlos Rafael Giani <dv@pseudoterminal.org>