xilinx-dp: Add support for the yuy2 video format

Add support for the yuy2 video format.

Reviewed-by: KONRAD Frederic <frederic.konrad@adacore.com>
Acked-by: Sai Pavan Boddu <saipava@xilinx.com>
Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>