Move aesni.h to library

`aesni.h` is an internal header and is moved accordingly.

Also removes some references to internal headers in scripts with
only public headers.

Signed-off-by: Chris Jones <christopher.jones@arm.com>
diff --git a/library/aesni.c b/library/aesni.c
index 996292f..be226c9 100644
--- a/library/aesni.c
+++ b/library/aesni.c
@@ -32,7 +32,7 @@
 #endif
 #endif
 
-#include "mbedtls/aesni.h"
+#include "aesni.h"
 
 #include <string.h>