linuxkpi: Move _RET_IP_ to <linux/instruction_pointer.h>

This matches the declaration on Linux.

Reviewed by:	bz, emaste
Sponsored by:	The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D55730

sys/compat/linuxkpi/common/include/linux/instruction_pointer.h

@@ -0,0 +1,13 @@
+/*
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2021 Neel Chauhan
+ * Copyright (c) 2026 The FreeBSD Foundation
+ */
+
+#ifndef	_LINUXKPI_LINUX_INSTRUCTION_POINTER_H_
+#define	_LINUXKPI_LINUX_INSTRUCTION_POINTER_H_
+
+#define	_RET_IP_		__builtin_return_address(0)
+
+#endif /* _LINUXKPI_LINUX_INSTRUCTION_POINTER_H_ */

sys/compat/linuxkpi/common/include/linux/kernel.h

@@ -55,6 +55,7 @@
 #include <linux/jiffies.h>
 #include <linux/log2.h>
 #include <linux/kconfig.h>
+#include <linux/instruction_pointer.h>
 
 #include <asm/byteorder.h>
 #include <asm/cpufeature.h>
@@ -267,8 +268,6 @@ extern int linuxkpi_debug;
 
 #define	u64_to_user_ptr(val)	((void *)(uintptr_t)(val))
 
-#define _RET_IP_		__builtin_return_address(0)
-
 #define offsetofend(t, m)	\
         (offsetof(t, m) + sizeof((((t *)0)->m)))