RDMA/iwcm: Remove unnecessary function argument

Remove unnecessary cm_id_priv argument to copy_private_data(), and
change text to reflect the code.  Fix couple of typos in comments.

Signed-off-by: Krishna Kumar <krkumar2@in.ibm.com>
Acked-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>