video: fsl_dcu_fb: add additional modes for DCU

Add common widescreen modes 800x480 and 1024x600.

Signed-off-by: Stefan Agner <stefan.agner@toradex.com>
Signed-off-by: Sanchayan Maity <maitysanchayan@gmail.com>
Reviewed-by: Alison Wang <alison.wang@nxp.com>