The credentials handling was pushed to the write handlers
but error handling wasn't done properly.
Move write callbacks to completion queue to destroy them
and to notify a blocked writer about the failure

Fixes: 136698e5 (mei: push credentials inside the irq write handler)
Signed-off-by: NAlexander Usyskin <alexander.usyskin@intel.com>
Signed-off-by: NTomas Winkler <tomas.winkler@intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>