drm/panel: samsung-s6e8aa0: Drop MIPI_DSI_MODE_VSYNC_FLUSH flag

Drop the MIPI_DSI_MODE_VSYNC_FLUSH flag from DSI mode_flags.
It has no effect anymore.

Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://lore.kernel.org/r/20250627-dsi-vsync-flush-v2-3-4066899a5608@pengutronix.de


Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>