drm/i915: reject modes the LPT FDI receiver can't handle

More specifically, the LPT FDI RX only supports 8bpc and a maximum of
2 lanes, so anything above that won't work and should be rejected.

Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 3915ca9..8a1bd4a 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -559,6 +559,7 @@
 			     enum pipe pipe);
 extern void intel_wait_for_vblank(struct drm_device *dev, int pipe);
 extern void intel_wait_for_pipe_off(struct drm_device *dev, int pipe);
+extern int ironlake_get_lanes_required(int target_clock, int link_bw, int bpp);
 
 struct intel_load_detect_pipe {
 	struct drm_framebuffer *release_fb;