drm: DRM_KMB_DISPLAY should select DRM_MIPI_DSI

drm: DRM_KMB_DISPLAY should select DRM_MIPI_DSI

If CONFIG_DRM_MIPI_DSI=n:

    aarch64-linux-gnu-ld: drivers/gpu/drm/kmb/kmb_dsi.o: in function `kmb_dsi_host_unregister':
    kmb_dsi.c:(.text+0xa48): undefined reference to `mipi_dsi_host_unregister'
    aarch64-linux-gnu-ld: drivers/gpu/drm/kmb/kmb_dsi.o: in function `kmb_dsi_host_bridge_init':
    kmb_dsi.c:(.text+0xb14): undefined reference to `mipi_dsi_host_register'

Fix this be selecting DRM_MIPI_DSI, like other drivers do.

Fixes: a1802de40c77ac6a ("drm/kmb: Build files for KeemBay Display driver")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20201110144219.3278831-1-geert+renesas@glider.be