drm/imx: add forward declarations for types

The imx.h header does not forward declare the types it uses, and the
header is not self-contained. Fix it.

Fixes: cc3e8a2 ("drm/imx: add internal bridge handling display-timings DT node")
Cc: Philipp Zabel <p.zabel@pengutronix.de>
Cc: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Cc: imx@lists.linux.dev
Cc: linux-arm-kernel@lists.infradead.org
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20241009140452.1981175-1-jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

include/drm/bridge/imx.h

@@ -6,6 +6,10 @@
 #ifndef DRM_IMX_BRIDGE_H
 #define DRM_IMX_BRIDGE_H
 
+struct device;
+struct device_node;
+struct drm_bridge;
+
 struct drm_bridge *devm_imx_drm_legacy_bridge(struct device *dev,
 					      struct device_node *np,
 					      int type);