drm/bridge: lt8912b: Fix DSI Video Mode

LT8912 DSI port supports only Non-Burst mode video operation with Sync
Events and continuous clock on clock lane, correct dsi mode flags
according to that removing MIPI_DSI_MODE_VIDEO_BURST flag.

Cc: <stable@vger.kernel.org>
Fixes: 30e2ae94

 ("drm/bridge: Introduce LT8912B DSI to HDMI bridge")
Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
Reviewed-by: Robert Foss <rfoss@kernel.org>
Signed-off-by: Robert Foss <rfoss@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230330093131.424828-1-francesco@dolcini.it