V4L/DVB (4508): Fix an array overflow on bt866

The Coverity checker spotted the following two array overflows.
Registers 0xcc and 0xdc were cached on reg[] array, with only 128 elements, 
instead of 256.
Signed-off-by: NMauro Carvalho Chehab <mchehab@infradead.org>

drivers/media/video/bt866.c

@@ -65,7 +65,7 @@ MODULE_LICENSE("GPL");
 struct bt866 {
 	struct i2c_client *i2c;
 	int addr;
-	unsigned char reg[128];
+	unsigned char reg[256];
 
 	int norm;
 	int enable;