#1 correct problem with refcnt

[Janice Girouard]

when __dev_get_by_name was changed to a call to
dev_get_by_name, the refcnt value was incremented
in the slave. A cooresponding decrement is required
and can be provided via dev_put call.

The symptom is that the system will not shutdown
problem when the refcnt is non-zero.