devices/pipe-rtt: Properly handle timeout in RTT reads

This change fixes the problem of plo's `wait` command not waiting while
using RTT console. Read operation was completed immediately instead of
blocking for at least `timeout`.

JIRA: NIL-596

devices/pipe-rtt/device.c

@@ -22,9 +22,20 @@
 static ssize_t pipe_read(unsigned int minor, addr_t offs, void *buff, size_t len, time_t timeout)
 {
 	(void)offs;
-	(void)timeout;
+	time_t start = hal_timerGet();
 
-	return rtt_read(minor + 1, buff, len);
+	while (1 == 1) {
+		ssize_t ret = rtt_read(minor + 1, buff, len);
+
+		if (ret != 0) {
+			return ret;
+		}
+		if ((hal_timerGet() - start) >= timeout) {
+			return -ETIME;
+		}
+	}
+
+	return 0;
 }