drm/imx: parallel-display: add legacy bridge Kconfig dependency

The driver now uses the legacy bridge helper code but can be configured
to get built without it:

ERROR: modpost: "devm_imx_drm_legacy_bridge" [drivers/gpu/drm/imx/ipuv3/parallel-display.ko] undefined!

Add the required dependency, same as in the ldb driver.

Fixes: f94b9707a1c9 ("drm/imx: parallel-display: switch to imx_legacy_bridge / drm_bridge_connector")
Signed-off-by: Arnd Bergmann <[e-mail]>
Reviewed-by: Dmitry Baryshkov <[e-mail]>
Signed-off-by: Robert Foss <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/imx/ipuv3/Kconfig

···
 	depends on DRM_IMX
 	select DRM_BRIDGE
 	select DRM_BRIDGE_CONNECTOR
+	select DRM_IMX_LEGACY_BRIDGE
 	select DRM_PANEL_BRIDGE
 	select VIDEOMODE_HELPERS