KVM: MIPS: Enable after disabling interrupt

Enable disabled interrupt, on unsuccessful operation.

Found by Coccinelle.

Signed-off-by: Tapasweni Pathak <tapaswenipathak@gmail.com>
Acked-by: Julia Lawall <julia.lawall@lip6.fr>
Reviewed-by: James Hogan <james.hogan@imgtec.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>