drm/bridge: cdns-dsi: Don't fail on MIPI_DSI_MODE_VIDEO_BURST

drm/bridge: cdns-dsi: Don't fail on MIPI_DSI_MODE_VIDEO_BURST

While the cdns-dsi does not support DSI burst mode, the burst mode is
essentially DSI event mode with more versatile clocking and timings.
Thus cdns-dsi doesn't need to fail if the DSI peripheral driver requests
MIPI_DSI_MODE_VIDEO_BURST.

In my particular use case, this allows the use of ti-sn65dsi83 driver.

Tested-by: Parth Pancholi <parth.pancholi@toradex.com>
Tested-by: Jayesh Choudhary <j-choudhary@ti.com>
Reviewed-by: Devarsh Thakkar <devarsht@ti.com>
Link: https://lore.kernel.org/r/20250723-cdns-dsi-impro-v5-15-e61cc06074c2@ideasonboard.com
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>