drm/mediatek/mtk_disp_ovl: Strip and demote non-conformant header

Fixes the following W=1 kernel build warning(s):

 drivers/gpu/drm/mediatek/mtk_disp_ovl.c:83: warning: Function parameter or member 'clk' not described in 'mtk_disp_ovl'
 drivers/gpu/drm/mediatek/mtk_disp_ovl.c:83: warning: Function parameter or member 'regs' not described in 'mtk_disp_ovl'
 drivers/gpu/drm/mediatek/mtk_disp_ovl.c:83: warning: Function parameter or member 'cmdq_reg' not described in 'mtk_disp_ovl'
 drivers/gpu/drm/mediatek/mtk_disp_ovl.c:83: warning: Function parameter or member 'vblank_cb' not described in 'mtk_disp_ovl'
 drivers/gpu/drm/mediatek/mtk_disp_ovl.c:83: warning: Function parameter or member 'vblank_cb_data' not described in 'mtk_disp_ovl'

Cc: Chun-Kuang Hu <[email protected]>
Cc: Philipp Zabel <[email protected]>
Cc: David Airlie <[email protected]>
Cc: Daniel Vetter <[email protected]>
Cc: Matthias Brugger <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Lee Jones <[email protected]>
Signed-off-by: Daniel Vetter <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

drivers/gpu/drm/mediatek/mtk_disp_ovl.c

@@ -66,9 +66,8 @@ struct mtk_disp_ovl_data {
 	bool smi_id_en;
 };
 
-/**
+/*
  * struct mtk_disp_ovl - DISP_OVL driver structure
- * @ddp_comp: structure containing type enum and hardware resources
  * @crtc: associated crtc to report vblank events to
  * @data: platform data
  */