telit: increase timeout for AT#REBOOT

It was observed that sporadically it may take more than 5 seconds for modem to
respond to AT#REBOOT. Increase the timeout on AT command to not report
unnecessary errors to the user.

plugins/telit/mm-broadband-modem-telit.c

@@ -710,7 +710,7 @@ modem_reset (MMIfaceModem *self,
 {
     mm_base_modem_at_command (MM_BASE_MODEM (self),
                               "AT#REBOOT",
-                              3,
+                              8,
                               FALSE,
                               callback,
                               user_data);