Revert "KVM: VMX: Save HOST_CR3 in vmx_set_host_fs_gs()"

Revert "KVM: VMX: Save HOST_CR3 in vmx_set_host_fs_gs()"

Undo a nested VMX fix as a step toward reverting the commit it fixed,
15ad9762d69f ("KVM: VMX: Save HOST_CR3 in vmx_prepare_switch_to_guest()"),
as the underlying premise that "host CR3 in the vcpu thread can only be
changed when scheduling" is wrong.

This reverts commit a9f2705ec84449e3b8d70c804766f8e97e23080d.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220224191917.3508476-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>