mei: use disconnect name consistently

Rename mei_cl_irq_close to mei_cl_irq_disconnect
and MEI_FOP_CLOSE to MEI_FOP_DISCONNECT
Remove unused MEI_FOP_OPEN

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