drm/i915: Clear unused fields of mode for framebuffer creation

With the stricter checks introduced in
commit ac911edae5960d7dccd9883f5fa5d25b591520de
Author: Ville Syrjälä <ville.syrjala@linux.intel.com>
Date:   Wed Oct 31 17:50:19 2012 +0200

    drm/i915: Check the framebuffer offset

(and friends), it became especially prudent to make sure that the
additional fields inside the mode were cleared before attempting to
create a framebuffer. In particular, the fb created for load detection
failed to do so and hence failed.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_display.c

@@ -6470,7 +6470,7 @@ intel_framebuffer_create_for_mode(struct drm_device *dev,
 				  int depth, int bpp)
 {
 	struct drm_i915_gem_object *obj;
-	struct drm_mode_fb_cmd2 mode_cmd;
+	struct drm_mode_fb_cmd2 mode_cmd = { 0 };
 
 	obj = i915_gem_alloc_object(dev,
 				    intel_framebuffer_size_for_mode(mode, bpp));