drm/rockchip/dw-mipi-dsi-rockchip: Demote non-conformant kernel-doc headers

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

 drivers/gpu/drm/rockchip/dw-mipi-dsi-rockchip.c:357: warning: Function parameter or member 'dsi' not described in 'ns2bc'
 drivers/gpu/drm/rockchip/dw-mipi-dsi-rockchip.c:357: warning: Function parameter or member 'ns' not described in 'ns2bc'
 drivers/gpu/drm/rockchip/dw-mipi-dsi-rockchip.c:365: warning: Function parameter or member 'dsi' not described in 'ns2ui'
 drivers/gpu/drm/rockchip/dw-mipi-dsi-rockchip.c:365: warning: Function parameter or member 'ns' not described in 'ns2ui'

Cc: Sandy Huang <hjc@rock-chips.com>
Cc: "Heiko Stübner" <heiko@sntech.de>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Chris Zhong <zyw@rock-chips.com>
Cc: Nickey Yang <nickey.yang@rock-chips.com>
Cc: dri-devel@lists.freedesktop.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-rockchip@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/20201116174112.1833368-25-lee.jones@linaro.org

drivers/gpu/drm/rockchip/dw-mipi-dsi-rockchip.c

@@ -350,7 +350,7 @@ static void dw_mipi_dsi_phy_write(struct dw_mipi_dsi_rockchip *dsi,
 	dsi_write(dsi, DSI_PHY_TST_CTRL0, PHY_TESTCLK | PHY_UNTESTCLR);
 }
 
-/**
+/*
  * ns2bc - Nanoseconds to byte clock cycles
  */
 static inline unsigned int ns2bc(struct dw_mipi_dsi_rockchip *dsi, int ns)
@@ -358,7 +358,7 @@ static inline unsigned int ns2bc(struct dw_mipi_dsi_rockchip *dsi, int ns)
 	return DIV_ROUND_UP(ns * dsi->lane_mbps / 8, 1000);
 }
 
-/**
+/*
  * ns2ui - Nanoseconds to UI time periods
  */
 static inline unsigned int ns2ui(struct dw_mipi_dsi_rockchip *dsi, int ns)