g_resize_provider_event: Do not invoke orphan method twice

Like r266444, g_resize_provider_event can attempt to orphan an already
orphaned geom_dev consumer. This will cause a panic in g_dev_orphan. Apply
the same fix as was applied to g_orphan_register.

Reviewed by: ae
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D12469