drmModeGetFB returns -EINVAL for multi-planar framebuffers. Instead of
depending on the framebuffer dimensions to select the mode, use width
and height from GstVideoInfo, which was used to create the framebuffer
in the first place. This enables kmssink to display multi-planar
formats such as I420 or NV12 with modesetting enabled.
https://bugzilla.gnome.org/show_bug.cgi?id=796985
62a194c781