KVM: nVMX: don't reset kvm mmu twice

kvm mmu is reset once successfully loading CR3 as part of emulating vmentry
in nested_vmx_load_cr3(). We should not reset kvm mmu twice.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>