add impl From<kvm_xsave> for kvm_xsave2

Construct an kvm_xsave2 with length set to 0. Useful when only a
kvm_xsave is at hand, but an API demands a kvm_xsave2, so the kvm_xsave
needs to converted into a Xsave with empty flexible array.

Signed-off-by: Patrick Roy <[email protected]>

Author: roypat

kvm-bindings/src/x86_64/fam_wrappers.rs

@@ -113,6 +113,12 @@ pub struct kvm_xsave2 {
     pub xsave: kvm_xsave,
 }
 
+impl From<kvm_xsave> for kvm_xsave2 {
+    fn from(xsave: kvm_xsave) -> Self {
+        kvm_xsave2 { len: 0, xsave }
+    }
+}
+
 // SAFETY:
 // - `kvm_xsave2` is a POD
 // - `kvm_xsave2` contains a flexible array member as its final field, due to `kvm_xsave` containing