KVM: SVM: Rename struct nested_state to svm_nested_state

Renaming is only needed in the svm.h header file.

No functional changes.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Message-Id: <20200625080325.28439-2-joro@8bytes.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>