RDMA/siw: Fix endpoint/socket association handling

In the Linux kernel, the following vulnerability has been resolved: RDMA/siw: Fix endpoint/socket association handling Disassociating a socket from an endpoint via siw_socket_disassoc() may release the last reference on that endpoint and free it. Therefore, don't clear the endpoints socket pointer after calling that function, but within. This fixes a: BUG: KASAN: slab-use-after-free in siw_cm_work_handler (drivers/infiniband/sw/siw/siw_cm.c:1053 drivers/infiniband/sw/siw/siw_cm.c:1075) which occurred after processing a malformed MPA request during connection establishment, causing the new endpoint to be closed.