IVGCVSW-7024 Add missing license info for reuse lint

Signed-off-by: Jim Flynn <jim.flynn@arm.com>
Change-Id: I97dee6982e0a7be01c13e9e803c0997547a39ff1
diff --git a/third-party/fmt/src/format.cc b/third-party/fmt/src/format.cc
index a64a1f3..10af1f5 100644
--- a/third-party/fmt/src/format.cc
+++ b/third-party/fmt/src/format.cc
@@ -2,6 +2,7 @@
 //
 // Copyright (c) 2012 - 2016, Victor Zverovich
 // All rights reserved.
+// SPDX-License-Identifier: MIT
 //
 // For the license information refer to format.h.