KVM: nVMX: Simplify the initialization of nested_vmx_msrs

The nested VMX controls MSRs can be initialized by the global capability
values stored in vmcs_config.

Signed-off-by: Chenyi Qiang <chenyi.qiang@intel.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Message-Id: <20200828085622.8365-6-chenyi.qiang@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>