Move license out of Doxygen comment

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/library/bignum_core.h b/library/bignum_core.h
index 8e227f8..dc802ab 100644
--- a/library/bignum_core.h
+++ b/library/bignum_core.h
@@ -6,6 +6,9 @@
  *  modules should use the high-level modular bignum interface (bignum_mod.h)
  *  or the legacy bignum interface (bignum.h).
  *
+ */
+
+/*
  *  Copyright The Mbed TLS Contributors
  *  SPDX-License-Identifier: Apache-2.0
  *
diff --git a/library/bignum_mod.h b/library/bignum_mod.h
index 9d28bc7..982a9ac 100644
--- a/library/bignum_mod.h
+++ b/library/bignum_mod.h
@@ -1,6 +1,8 @@
 /**
  *  Modular bignum functions
- *
+ */
+
+/*
  *  Copyright The Mbed TLS Contributors
  *  SPDX-License-Identifier: Apache-2.0
  *
diff --git a/library/bignum_mod_raw.h b/library/bignum_mod_raw.h
index 7b3a0c1..aba5d06 100644
--- a/library/bignum_mod_raw.h
+++ b/library/bignum_mod_raw.h
@@ -5,7 +5,9 @@
  *  module (bignum_mod.c) and the ECP module (ecp.c, ecp_curves.c). All other
  *  modules should use the high-level modular bignum interface (bignum_mod.h)
  *  or the legacy bignum interface (bignum.h).
- *
+ */
+
+/*
  *  Copyright The Mbed TLS Contributors
  *  SPDX-License-Identifier: Apache-2.0
  *