libceph: drop declaration of ceph_con_get()

commit 261030215d970c62f799e6e508e3c68fc7ec2aa9 upstream.

For some reason the declaration of ceph_con_get() and
ceph_con_put() did not get deleted in this commit:
    d59315ca libceph: drop ceph_con_get/put helpers and nref member

Clean that up.

Signed-off-by: Alex Elder <elder@inktank.com>
Cc: Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>