Add missing asterisk to doxygen closures

Clarify section names next to closing braces
Signed-off-by: Andrzej Kurek <andrzej.kurek@arm.com>
diff --git a/include/mbedtls/hkdf.h b/include/mbedtls/hkdf.h
index e6bfe05..2e225cb 100644
--- a/include/mbedtls/hkdf.h
+++ b/include/mbedtls/hkdf.h
@@ -35,7 +35,7 @@
  */
 /** Bad input parameters to function. */
 #define MBEDTLS_ERR_HKDF_BAD_INPUT_DATA  -0x5F80
-/* \} name */
+/** \} name */
 
 #ifdef __cplusplus
 extern "C" {