drm/xen-front: Add YUYV to supported formats

Add YUYV to supported formats, so the frontend can work with the
formats used by cameras and other HW.

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Acked-by: Noralf Trønnes <noralf@tronnes.org>
Link: https://lore.kernel.org/r/20200813062113.11030-4-andr2000@gmail.com


Signed-off-by: Juergen Gross <jgross@suse.com>