hv: intercept IA32_PAT MSR

Preparing for emulating guest's CR0.CD and CR0.NW bits:
 - Intercept both rdmsr and wrmsr for IA32_PAT
 - Track guest's IA32_PAT MSR with vcpu.arch_vcpu.contexts.ia32_pat

Signed-off-by: Zide Chen <zide.chen@intel.com>
Acked-by: Eddie Dong <eddie.dong@intel.com>

hypervisor/include/arch/x86/guest/guest.h

@@ -28,6 +28,7 @@ enum {
 	IDX_BIOS_UPDT_TRIG,
 	IDX_BIOS_SIGN_ID,
 	IDX_TSC,
+	IDX_PAT,
 
 	IDX_MAX_MSR
 };