This service test the file services data structures.
EBX address of error string (unless no error)
AL status (0 means ok, no error string)
0xFE Shutdown module
This de-allocates all resources used. Interrupts must be disabled before removing the file services, and they should not be enabled again until another file services has taken it's place. The code selector returned by this service should be de-allocated by the caller.
bx Code Selector