KVM: SVM: Make sure rip is synced to vmcb before nested vmexit

This patch fixes a bug where a nested guest always went over
the same instruction because the rip was not advanced on a
nested vmexit.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Avi Kivity <avi@redhat.com>