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/aes.c b/library/aes.c
index 3f61642..5201aed 100644
--- a/library/aes.c
+++ b/library/aes.c
@@ -37,7 +37,7 @@
 #include "mbedtls/padlock.h"
 #endif
 #if defined(MBEDTLS_AESNI_C)
-#include "mbedtls/aesni.h"
+#include "aesni.h"
 #endif
 
 #if defined(MBEDTLS_SELF_TEST)