drm: bridge: fix ANX7625 use of mipi_dsi_() functions

The Analogix DRM ANX7625 bridge driver uses mips_dsi_() function
interfaces so it should select DRM_MIPI_DSI to prevent build errors.

ERROR: modpost: "mipi_dsi_attach" [drivers/gpu/drm/bridge/analogix/anx7625.ko] undefined!
ERROR: modpost: "mipi_dsi_device_register_full" [drivers/gpu/drm/bridge/analogix/anx7625.ko] undefined!
ERROR: modpost: "of_find_mipi_dsi_host_by_node" [drivers/gpu/drm/bridge/analogix/anx7625.ko] undefined!
ERROR: modpost: "mipi_dsi_device_unregister" [drivers/gpu/drm/bridge/analogix/anx7625.ko] undefined!
ERROR: modpost: "mipi_dsi_detach" [drivers/gpu/drm/bridge/analogix/anx7625.ko] undefined!

Fixes: 8bdfc5da

 ("drm/bridge: anx7625: Add anx7625 MIPI DSI/DPI to DP")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Robert Foss <robert.foss@linaro.org>
Cc: Xin Ji <xji@analogixsemi.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: dri-devel@lists.freedesktop.org
Cc: Andrzej Hajda <a.hajda@samsung.com>
Cc: Neil Armstrong <narmstrong@baylibre.com>
Cc: Robert Foss <robert.foss@linaro.org>
Cc: stable@vger.kernel.org
Signed-off-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210415183619.1431-1-rdunlap@infradead.org