Change the format of md.h include comments

Signed-off-by: Andrzej Kurek <andrzej.kurek@arm.com>
diff --git a/programs/pkey/dh_client.c b/programs/pkey/dh_client.c
index be0b6e9..5a2c30f 100644
--- a/programs/pkey/dh_client.c
+++ b/programs/pkey/dh_client.c
@@ -20,6 +20,7 @@
 #include "mbedtls/build_info.h"
 
 #include "mbedtls/platform.h"
+/* md.h is included this early since MD_CAN_XXX macros are defined there. */
 #include "mbedtls/md.h"
 
 #if defined(MBEDTLS_AES_C) && defined(MBEDTLS_DHM_C) && \