RDMA/siw: Introduce siw_destroy_cep_sock

Add one helper to simplify code a bit.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202310091735.oG7bTvLR-lkp@intel.com/`


Acked-by: Bernard Metzler <bmt@zurich.ibm.com>
Signed-off-by: Guoqing Jiang <guoqing.jiang@linux.dev>
Link: https://lore.kernel.org/r/20231113115726.12762-17-guoqing.jiang@linux.dev


Signed-off-by: Leon Romanovsky <leon@kernel.org>