mei: connection to fixed address clients from user-space

This should be used for debug only.
The feaure is gated by "allow_fixed_address" control exposed in debugfs.

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