drm/i915: Use CONFIG_DRM_FBDEV_EMULATION

Instead of our own duplicated one. This fixes a bug in the driver
unload code if DRM_FBDEV_EMULATION=n but DRM_I915_FBDEV=y because we
try to unregister the nonexistent fbdev drm_framebuffer.

Cc: Archit Taneja <architt@codeaurora.org>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reported-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 23ce125e..e9d2bef 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1854,7 +1854,7 @@
 
 	struct drm_i915_gem_object *vlv_pctx;
 
-#ifdef CONFIG_DRM_I915_FBDEV
+#ifdef CONFIG_DRM_FBDEV_EMULATION
 	/* list of fbdev register on this device */
 	struct intel_fbdev *fbdev;
 	struct work_struct fbdev_suspend_work;