Move free_nested() down below vmx_switch_vmcs() so that a future patch
can do an "emergency" invocation of vmx_switch_vmcs() if vmcs01 is not
the loaded VMCS when freeing nested resources.

No functional change intended.
Signed-off-by: NSean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20200923184452.980-5-sean.j.christopherson@intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>