ila: fix potential snprintf buffer overflow

The code to print 64 bit address has a theoretical overflow
of snprintf buffer found by CodeQL scan.
Address by checking result.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>

ip/ipila.c

@@ -60,6 +60,8 @@ static void print_addr64(__u64 addr, char *buff, size_t len)
 			sep = "";
 
 		ret = snprintf(&buff[written], len - written, "%x%s", v, sep);
+		if (ret < 0 || ret >= len - written)
+			break;
 		written += ret;
 	}
 }