adv7842: comment out a table useful for debug

Gcc 6.1 warns about an unused table:

drivers/media/i2c/adv7842.c:2400:27: warning: 'prim_mode_txt' defined but not used [-Wunused-const-variable=]
 static const char * const prim_mode_txt[] = {
                           ^~~~~~~~~~~~~

That seems to be useful for debug, and likely were used before.
While we could simply remove, let's comment it out, for now.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/i2c/adv7842.c

@@ -2397,6 +2397,8 @@ static void adv7842_log_infoframes(struct v4l2_subdev *sd)
 		log_infoframe(sd, &cri[i]);
 }
 
+#if 0
+/* Let's keep it here for now, as it could be useful for debug */
 static const char * const prim_mode_txt[] = {
 	"SDP",
 	"Component",
@@ -2415,6 +2417,7 @@ static const char * const prim_mode_txt[] = {
 	"Reserved",
 	"Reserved",
 };
+#endif
 
 static int adv7842_sdp_log_status(struct v4l2_subdev *sd)
 {