drm: xlnx: zynqmp_dpsub: Anounce supported input formats

DPSUB in bridge mode supports multiple input media bus formats.

Announce the list of supported input media bus formats via
drm_bridge.atomic_get_input_bus_fmts callback. Introduce a set of live
input formats supported by DPSUB. Add safeguards to format list functions
to prevent their misuse in the different layer modes contexts.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Anatoliy Klymenko <anatoliy.klymenko@amd.com>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240416-dp-live-fmt-v4-4-c7f379b7168e@amd.com