sierra: avoid reset when setting cfun=1

Some Sierra modems trigger a reset of the modem when sending +cfun=1.
All sierra modems supports a second parameter to indicate that no
reset is to be done: "+cfun=1,0".

plugins/sierra/mm-common-sierra.c

@@ -115,7 +115,7 @@ get_current_functionality_status_ready (MMBaseModem *self,
      * Works well if we previously switched off the power with CFUN=4
      */
     mm_base_modem_at_command (MM_BASE_MODEM (self),
-                              "+CFUN=1",
+                              "+CFUN=1,0", /* ",0" ensures no reset */
                               3,
                               FALSE,
                               (GAsyncReadyCallback)full_functionality_status_ready,