Revert r222135 by allowing controller reinitialization. Due to

unknown reason Apple UniNorth2 gem(4) device required manual
interface down/up operation after r222135.  Even though this is not
correct thing and I don't like to revert it but it would be better
than breaking gem(4) on PPC.  This should be revisited.

PR:	kern/157405

sys/dev/gem/if_gem.c

@@ -947,8 +947,10 @@ gem_init_locked(struct gem_softc *sc)
 
 	GEM_LOCK_ASSERT(sc, MA_OWNED);
 
+#ifdef notyet
 	if ((ifp->if_drv_flags & IFF_DRV_RUNNING) != 0)
 		return;
+#endif
 
 #ifdef GEM_DEBUG
 	CTR2(KTR_GEM, "%s: %s: calling stop", device_get_name(sc->sc_dev),