chelsio/chtls: fix writing freed memory

When chtls_sock *csk is freed, same memory can be allocated
to different csk in chtls_sock_create().
csk->cdev = NULL; statement might ends up modifying wrong
csk, eventually causing kernel panic.
removing (csk->cdev = NULL) statement as it is not required.

Fixes: 3a0a9783 ("crypto/chtls: Fix chtls crash in connection cleanup")
Signed-off-by: Vinay Kumar Yadav <vinay.yadav@chelsio.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>