vdso: Introduce vdso/align.h

The vDSO implementation can only include headers from the vdso/
namespace. To enable the usage of the ALIGN() macro from the vDSO, move
linux/align.h to vdso/align.h wholly.
As the only dependency linux/const.h is only a wrapper around
vdso/const.h anyways adapt that dependency.

Also provide a compatibility wrapper linux/align.h.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250204-vdso-store-rng-v3-3-13a4669dfc8c@linutronix.de

Author: t-8ch

include/linux/align.h

@@ -2,14 +2,6 @@
 #ifndef _LINUX_ALIGN_H
 #define _LINUX_ALIGN_H
 
-#include <linux/const.h>
-
-/* @a is a power of 2 value */
-#define ALIGN(x, a)		__ALIGN_KERNEL((x), (a))
-#define ALIGN_DOWN(x, a)	__ALIGN_KERNEL((x) - ((a) - 1), (a))
-#define __ALIGN_MASK(x, mask)	__ALIGN_KERNEL_MASK((x), (mask))
-#define PTR_ALIGN(p, a)		((typeof(p))ALIGN((unsigned long)(p), (a)))
-#define PTR_ALIGN_DOWN(p, a)	((typeof(p))ALIGN_DOWN((unsigned long)(p), (a)))
-#define IS_ALIGNED(x, a)		(((x) & ((typeof(x))(a) - 1)) == 0)
+#include <vdso/align.h>
 
 #endif	/* _LINUX_ALIGN_H */

include/vdso/align.h

@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __VDSO_ALIGN_H
+#define __VDSO_ALIGN_H
+
+#include <vdso/const.h>
+
+/* @a is a power of 2 value */
+#define ALIGN(x, a)		__ALIGN_KERNEL((x), (a))
+#define ALIGN_DOWN(x, a)	__ALIGN_KERNEL((x) - ((a) - 1), (a))
+#define __ALIGN_MASK(x, mask)	__ALIGN_KERNEL_MASK((x), (mask))
+#define PTR_ALIGN(p, a)		((typeof(p))ALIGN((unsigned long)(p), (a)))
+#define PTR_ALIGN_DOWN(p, a)	((typeof(p))ALIGN_DOWN((unsigned long)(p), (a)))
+#define IS_ALIGNED(x, a)		(((x) & ((typeof(x))(a) - 1)) == 0)
+
+#endif	/* __VDSO_ALIGN_H */