Add links for macros in doxygen documentation

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
diff --git a/include/mbedtls/mbedtls_config.h b/include/mbedtls/mbedtls_config.h
index b1c9db9..3c5a284 100644
--- a/include/mbedtls/mbedtls_config.h
+++ b/include/mbedtls/mbedtls_config.h
@@ -2644,7 +2644,7 @@
  * \def MBEDTLS_MD_C
  *
  * Enable the generic layer for message digest (hashing) and HMAC.
- * This will automatically enabled MBEDTLS_MD_LIGHT
+ * This will automatically enable #MBEDTLS_MD_LIGHT
  *
  * Requires: one of: MBEDTLS_MD5_C, MBEDTLS_RIPEMD160_C, MBEDTLS_SHA1_C,
  *                   MBEDTLS_SHA224_C, MBEDTLS_SHA256_C, MBEDTLS_SHA384_C,
@@ -2676,11 +2676,11 @@
 /**
  * \def MBEDTLS_MD_LIGHT
  *
- * Enable the "light" subset of MBEDTLS_MD_C: just hashing and basic
+ * Enable the "light" subset of #MBEDTLS_MD_C: just hashing and basic
  * meta-data (see md.h for details).
  *
- * This is automatically enabled whenever MBEDTLS_MD_C is enabled, but it is
- * possible to enable this without MBEDTLS_MD_C if support for HMAC or extra
+ * This is automatically enabled whenever #MBEDTLS_MD_C is enabled, but it is
+ * possible to enable this without #MBEDTLS_MD_C if support for HMAC or extra
  * metadata functions is not needed.
  *
  * Requires: one of: MBEDTLS_MD5_C, MBEDTLS_RIPEMD160_C, MBEDTLS_SHA1_C,
diff --git a/include/mbedtls/md.h b/include/mbedtls/md.h
index 013cb65..e3561ba 100644
--- a/include/mbedtls/md.h
+++ b/include/mbedtls/md.h
@@ -6,12 +6,12 @@
  *
  *          Availability of functions in this modules is controled by two
  *          feature macros:
- *          - MBEDTLS_MD_C enables the whole module;
- *          - MBEDTLS_MD_LIGHT enables only functions for hashing and accessing
+ *          - #MBEDTLS_MD_C enables the whole module;
+ *          - #MBEDTLS_MD_LIGHT enables only functions for hashing and accessing
  *          most hash metadata (everything except string names); is it
- *          automatically set whenever MBEDTLS_MD_C is defined.
+ *          automatically set whenever #MBEDTLS_MD_C is defined.
  *
- *          The functions that are only available when MBEDTLS_MD_C is defined
+ *          The functions that are only available when #MBEDTLS_MD_C is defined
  *          are grouped at the end of the file and guarded by this macro.
  *
  * \author Adriaan de Jong <dejong@fox-it.com>