mei: split amthif client init from end of clients enumeration

The amthif FW client can appear after the end of client enumeration.
Amthif host client initialization is done now at FW client discovery
time.

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>