ANDROID: pkvm: vmx: Enable the CPU vulnerabilities mitigation code for vmenter.S

Previously the pkvm has a copy of kvm's vmenter.S with the CPU
vulnerabilities mitigation code disabled for simplify. Enable these
mitigations to guarantee the security.

After these mitigations being enabled, the vmenter.S in the pkvm is much
similar with the vmenter.S in kvm/vmx. So reuse the kvm/vmx/vmenter.S
for the pkvm hypervisor. New symbols are added in the pkvm hypervisor to
support enabling the mitigations used by the vmetner.S

Bug: 420681877
Upstream-Task: 402758258

Change-Id: I5f3c96c71fd25fff2adc9d50e5dff06a9446875a
Signed-off-by: Chuanxiao Dong <chuanxiao.dong@intel.com>