probe: fix probing on PPC due to missing cast

gcc will interpret the constant value as a uint32 but
the port's set_property() was taking it as a uint64.  Thus
the top 32 bits were probably garbage, and messed up
on big-endian architectures leading to random large
probe delays.

src/mm-plugin-base.c

@@ -489,7 +489,7 @@ mm_plugin_base_probe_port (MMPluginBase *self,
 
     serial = mm_serial_port_new (name, MM_PORT_TYPE_PRIMARY);
     g_object_set (serial,
-                  MM_SERIAL_PORT_SEND_DELAY, 100000,
+                  MM_SERIAL_PORT_SEND_DELAY, (guint64) 100000,
                   MM_PORT_CARRIER_DETECT, FALSE,
                   NULL);