drm/mediatek/mtk_disp_gamma: Strip and demote non-conformant kernel-doc header

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

 drivers/gpu/drm/mediatek/mtk_disp_gamma.c:42: warning: Function parameter or member 'clk' not described in 'mtk_disp_gamma'
 drivers/gpu/drm/mediatek/mtk_disp_gamma.c:42: warning: Function parameter or member 'regs' not described in 'mtk_disp_gamma'
 drivers/gpu/drm/mediatek/mtk_disp_gamma.c:42: warning: Function parameter or member 'cmdq_reg' not described in 'mtk_disp_gamma'
 drivers/gpu/drm/mediatek/mtk_disp_gamma.c:42: warning: Function parameter or member 'data' not described in 'mtk_disp_gamma'

Cc: Chun-Kuang Hu <chunkuang.hu@kernel.org>
Cc: Philipp Zabel <p.zabel@pengutronix.de>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Cc: dri-devel@lists.freedesktop.org
Cc: linux-mediatek@lists.infradead.org
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210602143300.2330146-3-lee.jones@linaro.org

drivers/gpu/drm/mediatek/mtk_disp_gamma.c

@@ -29,10 +29,8 @@ struct mtk_disp_gamma_data {
 	bool has_dither;
 };
 
-/**
+/*
  * struct mtk_disp_gamma - DISP_GAMMA driver structure
- * @ddp_comp - structure containing type enum and hardware resources
- * @crtc - associated crtc to report irq events to
  */
 struct mtk_disp_gamma {
 	struct clk *clk;