video: remove unused kconfig SH_LCD_MIPI_DSI

SH_LCD_MIPI_DSI is unused since commit 18b6562c ("fbdev: sh_mipi_dsi:
remove driver") so no need to keep it.

Fixes: 18b6562c ("fbdev: sh_mipi_dsi: remove driver")
Signed-off-by: Corentin Labbe <clabbe.montjoie@gmail.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>