samsung: split initialization sequence to ensure echo is off

Split the Samsung initialization sequence from "ATZ E0 V1" to "ATZ"
and "ATE0 V1" - the modem is allowed to ignore the rest of the line
after Z, so echoing was not being turned off, leading to getting
"AT+CIMI\n\n" as part of the IMSI when it is retrieved at startup.

Chromium:
Change-Id: Icfd767174e779e472f8cde419acb163128e4715d

plugins/mm-modem-samsung-gsm.c

@@ -504,6 +504,21 @@ init_done (MMAtSerialPort *port,
     }
 }
 
+static void
+init_reset_done (MMAtSerialPort *port,
+           GString *response,
+           GError *error,
+           gpointer user_data)
+{
+    MMCallbackInfo *info = (MMCallbackInfo *) user_data;
+    MMModemSamsungGsm *self = MM_MODEM_SAMSUNG_GSM (info->modem);
+
+    if (error)
+        mm_generic_gsm_enable_complete (MM_GENERIC_GSM (self), error, info);
+    else
+        mm_at_serial_port_queue_command (port, "E0 V1", 3, init_done, info);
+}
+
 static void
 do_enable (MMGenericGsm *modem, MMModemFn callback, gpointer user_data)
 {
@@ -514,7 +529,7 @@ do_enable (MMGenericGsm *modem, MMModemFn callback, gpointer user_data)
 
     primary = mm_generic_gsm_get_at_port (modem, MM_PORT_TYPE_PRIMARY);
     g_assert (primary);
-    mm_at_serial_port_queue_command (primary, "Z E0 V1", 3, init_done, info);
+    mm_at_serial_port_queue_command (primary, "Z", 3, init_reset_done, info);
 }
 
 static void