drivers/telephony/ixj: fix an array overrun

The Coverity checker noted that in
drivers/telephony/ixj.c:ixj_build_filter_cadence(), filter_en[4] or
filter_en[5] could be written to.
Signed-off-by: Adrian Bunk <bunk@stusta.de>

drivers/telephony/ixj.h

@@ -1295,7 +1295,7 @@ typedef struct {
 	Proc_Info_Type Info_write;
 	unsigned short frame_count;
 	unsigned int filter_hist[4];
-	unsigned char filter_en[4];
+	unsigned char filter_en[6];
 	unsigned short proc_load;
 	unsigned long framesread;
 	unsigned long frameswritten;