rust: Add missing license headers

Command used:

 $ rg --files-without-match --type rust '^// SPDX-Licen' --null | xargs -0 -I {} sed -i '1 i\// SPDX-License-Identifier: MIT\n//\n// Copyright IBM Corp. 2024\n' {}

Reviewed-by: Julian Ruess <julianr@linux.ibm.com>
Signed-off-by: Marc Hartmayer <mhartmay@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>

rust/pv/src/uvattest.rs

@@ -1,3 +1,7 @@
+// SPDX-License-Identifier: MIT
+//
+// Copyright IBM Corp. 2024
+
 pub mod additional;
 pub mod arcb;
 pub mod attest;

rust/pv/src/uvsecret/user_data.rs

@@ -1,3 +1,7 @@
+// SPDX-License-Identifier: MIT
+//
+// Copyright IBM Corp. 2024
+
 use crate::assert_size;
 use crate::{
     crypto::{sign_msg, verify_signature},

rust/pvsecret/src/cmd/verify.rs

@@ -1,3 +1,7 @@
+// SPDX-License-Identifier: MIT
+//
+// Copyright IBM Corp. 2024
+
 use crate::cli::VerifyOpt;
 use anyhow::{anyhow, Context, Result};
 use log::warn;