x86/VMX: fix VMCS setting for x2APIC mode guest while enabling APICV

x86/VMX: fix VMCS setting for x2APIC mode guest while enabling APICV

The "APIC-register virtualization" and "virtual-interrupt deliver"
VM-execution control has no effect on the behavior of RDMSR/WRMSR if
the "virtualize x2APIC mode" VM-execution control is 0.
When guest uses x2APIC mode, we should enable "virtualize x2APIC mode"
for APICV first.

Signed-off-by: Jiongxi Li <jiongxi.li@intel.com>
Acked-by: Eddie Dong <eddie.dong@intel.com>
Acked-by: Jun Nakajima <jun.nakajima@intel.com>
Committed-by: Jan Beulich <jbeulich@suse.com>