hypervisor: Add a basic implementation of MshvVcpuState for aarch64

Currently we are just storing the StandardRegisters in the Vcpu state
which would be required for saving and restoring the ARM64 guest on
MSHV.

Signed-off-by: Jinank Jain <jinankjain@microsoft.com>

hypervisor/src/lib.rs

@@ -163,7 +163,7 @@ pub enum IoEventAddress {
 pub enum CpuState {
     #[cfg(feature = "kvm")]
     Kvm(kvm::VcpuKvmState),
-    #[cfg(all(feature = "mshv", target_arch = "x86_64"))]
+    #[cfg(feature = "mshv")]
     Mshv(mshv::VcpuMshvState),
 }