detect_apicv_cap should used to detect all the APICv capabilities. Besides,
"Virtualize x2APIC mode" doesn't depend on "APIC-register virtualization".
We shouldn't check "Virtualize x2APIC mode" support only when physical platform
supports "APIC-register virtualization"
Tracked-On: #1842
Signed-off-by: Li, Fei1 <fei1.li@intel.com>