Fix generic driver not attaching to virtual ports

Since c2e3a8c10e, the generic plugin was
not able to attach to virtual ports, because they have no associated
driver, and the probe fails with "port filtered as couldn't retrieve
driver". It seems that this driver check was accidentially introduced
and is not really necessary, as there isn't a special "XMMRPC driver"
to blacklist.

Signed-off-by: Sonya Sireneva <sleirsgoevy@gmail.com>

src/mm-plugin.c

@@ -285,8 +285,7 @@ apply_pre_probing_filters (MMPlugin       *self,
     if (self->priv->drivers ||
         self->priv->forbidden_drivers ||
         !self->priv->qmi ||
-        !self->priv->mbim ||
-        !self->priv->xmmrpc) {
+        !self->priv->mbim) {
         static const gchar *virtual_drivers [] = { "virtual", NULL };
         const gchar **drivers;