MLK-16375-3 video: fbdev: dcss: add '__maybe_unused' to 'fill_db'

The function 'fill_db()' is not used at this moment
which caused gcc compiler generate the build warning:

"‘fill_db’ defined but not used [-Wunused-function]"

So add attribute '__maybe_unused' to 'fill_db()' functon
definition to avoid this build warning.

Signed-off-by: Fancy Fang <chen.fang@nxp.com>

drivers/video/fbdev/mxc/imx_dcss.c

@@ -674,9 +674,9 @@ static void fill_sb(struct cbuffer *cb,
 	cb->sb_data_len++;
 }
 
-static void fill_db(struct cbuffer *cb,
-		    uint32_t offset,
-		    uint32_t value)
+static void __maybe_unused fill_db(struct cbuffer *cb,
+				   uint32_t offset,
+				   uint32_t value)
 {
 	struct ctxld_unit *unit = NULL;