Currently the dp_link address is provided to CDP vdev
as a part of vdev register. Also, as per the vdev deletion
sequence, it is possible that dp_link can be destroyed
before CDP vdev is detached. This can lead to use-after-free
scenario when CDP vdev uses the osif_vdev handle (which is
the dp_link handle).
In order to fix this, do not free the dp_link till the CDP
vdev has been detached.
Change-Id: Ie5a1140a0d256b6115fa62e30e6bfd61d1dfc898
CRs-Fixed: 3696641
c3b0114600