quectel: decrease low-power/power-on/reset wait times to 15 seconds

AT docs for many (most?) device state a max timeout of 15 seconds.

Signed-off-by: Dan Williams <dan@ioncontrol.co>

src/plugins/quectel/mm-broadband-modem-quectel.c

@@ -272,7 +272,7 @@ common_modem_power_operation (MMBroadbandModemQuectel  *self,
 {
     mm_base_modem_at_command (MM_BASE_MODEM (self),
                               command,
-                              30,
+                              15,
                               FALSE,
                               callback,
                               user_data);