mei: normalize me host client linking routines

In order we can use the same code pattern for in-kernel
and user space host clients we replace mei_cl_link_to_me
with mei_cl_link function.
We then have to keep me client lookupout of the new link function.

The unlinking cannot be yet symetric due to amthif connection
handling

Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>