[SCSI] libfcoe: VN2VN connection setup causing stack memory corruption.

Fix: When FIP frame is received, function fcoe_ctlr_vn_recv calls function
fcoe_ctlr_vn_parse which does memset for addr (&buf.rdata) which leads to
memory corruption. Code was trying to treat "buf" as struct but it was defined
as union. Fix is to change from union to struct for "buf" in function fcoe_ctlr_vn_recv.

Technical Details: N/A

Signed-off-by: Kiran Patil <kiran.patil@intel.com>
Acked-by: Joe Eykholt <jeykholt@cisco.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>