s390/cio: Use generalized CCW handler in cp_init()

It is now pretty apparent that ccwchain_handle_ccw()
(nee ccwchain_handle_tic()) does everything that cp_init()
wants to do.

Let's remove that duplicated code from cp_init() and let
ccwchain_handle_ccw() handle it itself.

Signed-off-by: Eric Farman <farman@linux.ibm.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Message-Id: <20190606202831.44135-5-farman@linux.ibm.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>