cxgb4: do not set needs_free_netdev for mgmt dev's

[ Upstream commit b06ef18a4c255609388ed6e068a1c69c797545e0 ]

Do not set 'needs_free_netdev' as we do call free_netdev
for mgmt net devices, doing both hits BUG_ON.

Signed-off-by: Ganesh Goudar <ganeshgr@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>