core: new kernel device object instead of an explicit GUdevDevice

Instead of relying constantly on GUdevDevice objects reported by GUdev, we now
use a new generic object (MMKernelDevice) for which we provide an initial GUdev
based backend.

plugins/haier/mm-plugin-haier.c

@@ -52,13 +52,13 @@ grab_port (MMPlugin *self,
            MMPortProbe *probe,
            GError **error)
 {
-    GUdevDevice *port;
+    MMKernelDevice *port;
     MMPortSerialAtFlag pflags = MM_PORT_SERIAL_AT_FLAG_NONE;
 
     port = mm_port_probe_peek_port (probe);
 
     /* Look for port type hints */
-    if (mm_port_probe_is_at (probe) && g_udev_device_get_property_as_boolean (port, "ID_MM_HAIER_PORT_TYPE_MODEM")) {
+    if (mm_port_probe_is_at (probe) && mm_kernel_device_get_property_as_boolean (port, "ID_MM_HAIER_PORT_TYPE_MODEM")) {
         mm_dbg ("HAIER: AT port '%s/%s' flagged as primary",
                 mm_port_probe_get_port_subsys (probe),
                 mm_port_probe_get_port_name (probe));