[media] gspca_zc3xx: Disable the highest quality setting as it is not usable

Even with BRC the highest quality setting is not usable, BRC strips so
much data from each MCU that the quality becomes worse then using a lower
quality setting to begin with.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/gspca/zc3xx.c

@@ -194,7 +194,7 @@ static const struct ctrl sd_ctrls[NCTRLS] = {
 		.type    = V4L2_CTRL_TYPE_INTEGER,
 		.name    = "Compression Quality",
 		.minimum = 50,
-		.maximum = 94,
+		.maximum = 87,
 		.step    = 1,
 		.default_value = 75,
 	    },
@@ -241,8 +241,11 @@ static const struct v4l2_pix_format sif_mode[] = {
 		.priv = 0},
 };
 
-/* bridge reg08 bits 1-2 -> JPEG quality conversion table */
-static u8 jpeg_qual[] = {50, 75, 87, 94};
+/*
+ * Bridge reg08 bits 1-2 -> JPEG quality conversion table. Note the highest
+ * quality setting is not usable as USB 1 does not have enough bandwidth.
+ */
+static u8 jpeg_qual[] = {50, 75, 87, /* 94 */};
 
 /* usb exchanges */
 struct usb_action {