hypervisor: Implement StandardRegisters as union of KVM & MSHV

Currently we are redefining StandardRegisters instead of using the ones
coming from bindings. With this we can remove the unnecessary
construction of global structure which contains fields from different
hypervisor dependent structs.

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

hypervisor/src/lib.rs

@@ -187,3 +187,11 @@ pub enum IrqRoutingEntry {
     #[cfg(feature = "mshv")]
     Mshv(mshv_bindings::mshv_msi_routing_entry),
 }
+
+#[derive(Debug, Clone, Copy, PartialEq, serde::Serialize, serde::Deserialize)]
+pub enum StandardRegisters {
+    #[cfg(feature = "kvm")]
+    Kvm(kvm_bindings::kvm_regs),
+    #[cfg(all(feature = "mshv", target_arch = "x86_64"))]
+    Mshv(mshv_bindings::StandardRegisters),
+}