drm/panel/panel-sitronix-st7701: Demote kernel-doc abuse

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

 drivers/gpu/drm/panel/panel-sitronix-st7701.c:42: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst

Cc: Jagan Teki <jagan@amarulasolutions.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: dri-devel@lists.freedesktop.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/20210602143300.2330146-22-lee.jones@linaro.org
Link: https://patchwork.freedesktop.org/patch/msgid/20210602143300.2330146-23-lee.jones@linaro.org

drivers/gpu/drm/panel/panel-sitronix-st7701.c

@@ -38,7 +38,7 @@
 #define DSI_CMD2_BK1_SPD2		0xC2 /* Source EQ2 Setting */
 #define DSI_CMD2_BK1_MIPISET1		0xD0 /* MIPI Setting 1 */
 
-/**
+/*
  * Command2 with BK function selection.
  *
  * BIT[4, 0]: [CN2, BKXSEL]