KVM: SVM: move nested svm state into seperate struct

This makes it more clear for which purpose these members in the vcpu_svm
exist.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Acked-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>