pseries: Fix use of global CPU state

pseries: Fix use of global CPU state

Commit ed120055c7f9b26b5707d3ceabbe5a3f06aaf937 (Implement PAPR VPA
functions for pSeries shared processor partitions) introduced the
deregister_dtl() function and typo "emv" as name of its argument.
This went unnoticed because the code in that function can access the
global variable "env" so that no build failure resulted.

Fix the argument to read "env". Resolves LP#986241.

Signed-off-by: Peter Portante <peter.portante@redhat.com>
Acked-by: Andreas Färber <afaerber@suse.de>
[agraf: fixed typo in commit message]
Signed-off-by: Alexander Graf <agraf@suse.de>