v3: Add the instance token check.
v2: The DHCP Instance might be destroyed in PxeDhcpDone. So,
we need safe-delete.
REF: https://bugzilla.tianocore.org/show_bug.cgi?id=1469
Since the value of Instance is retrieved from the list Entry,
it can't be the NULL pointer, so just remove the unnecessary
check.
Cc: Ye Ting <ting.ye@intel.com>
Cc: Fu Siyuan <siyuan.fu@intel.com>
Cc: Wu Hao A <hao.a.wu@intel.com>
Cc: Gao Liming <liming.gao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Wu Jiaxin <jiaxin.wu@intel.com>
Reviewed-by: Wu Hao A <hao.a.wu@intel.com>
710962016b