Silence a build warning. (chan_phone.c:810: warning: value computed is not used)

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@160171 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_phone.c

@@ -807,7 +807,7 @@ static int phone_write(struct ast_channel *ast, struct ast_frame *frame)
 		   we have to pad it to 24 bytes still.  */
 		if (frame->datalen == 4) {
 			if (p->silencesupression) {
-				memset(tmpbuf + 4, 0, sizeof(tmpbuf) - 4);
+				(void) memset(tmpbuf + 4, 0, sizeof(tmpbuf) - 4);
 				memcpy(tmpbuf, frame->data.ptr, 4);
 				expected = 24;
 				res = phone_write_buf(p, tmpbuf, expected, maxfr, 0);