mei: add mei_stop function to stop mei device

mei_stop calls mei_reset with disabling the interrupts.
It will have the same effect as the open code it replaces in the mei_remove.

The reset sequence on remove is required for the Lynx Point LP devices
to clean the reset state.

mei_stop is called from mei_pci_suspend and mei_remove functions

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