drm/fb-helper: Fix missing kerneldoc include

This was lost in the code movement done in commit 8ab59da
("drm/fb-helper: Move generic fbdev emulation into separate source
file").

Fixes: 8ab59da ("drm/fb-helper: Move generic fbdev emulation into separate source file")
Cc: Thomas Zimmermann <[email protected]>
Cc: Javier Martinez Canillas <[email protected]>
Reviewed-by: Thomas Zimmermann <[email protected]>
Signed-off-by: Daniel Vetter <[email protected]>
Signed-off-by: Thomas Zimmermann <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

Author: danvet

Documentation/gpu/drm-kms-helpers.rst

@@ -116,6 +116,9 @@ fbdev Helper Functions Reference
 .. kernel-doc:: drivers/gpu/drm/drm_fb_helper.c
    :export:
 
+.. kernel-doc:: drivers/gpu/drm/drm_fbdev_generic.c
+   :export:
+
 format Helper Functions Reference
 =================================