Rename ssl_internal.h to ssl_misc.h

Signed-off-by: Chris Jones <christopher.jones@arm.com>
diff --git a/library/ssl_cookie.c b/library/ssl_cookie.c
index 0824cd9..fa89a07 100644
--- a/library/ssl_cookie.c
+++ b/library/ssl_cookie.c
@@ -33,7 +33,7 @@
 #endif
 
 #include "mbedtls/ssl_cookie.h"
-#include "ssl_internal.h"
+#include "ssl_misc.h"
 #include "mbedtls/error.h"
 #include "mbedtls/platform_util.h"