src: Update macro guard name

Change macro guard name for `include/internal/types.h` from
`__TYPES_H__` to `__INTERNAL_TYPES_H__`. This prevents it from clashing
with the macro guard for `include/sys/types.h`.

Unless this change is applied, the inclusion of `sys/types.h` will not
lead to the inclusion of `internal/types.h`, since the macro guard
`__TYPES_H__` is used in both.

Signed-off-by: Razvan Deaconescu <razvan.deaconescu@upb.ro>

src/include/internal/types.h

 /* SPDX-License-Identifier: BSD-3-Clause */
 
-#ifndef __TYPES_H__
-#define __TYPES_H__	1
+#ifndef __INTERNAL_TYPES_H__
+#define __INTERNAL_TYPES_H__	1
 
 typedef unsigned long size_t;
 typedef long ssize_t;