LinuxKPI: cleanup: implement __free() and DEFINE_FREE(); use for kfree()

A wifi driver update needs this.

Sponsored by:	The FreeBSD Foundation (initially)
MFC after:	3 days
Reviewed by:	dumbbell
Differential Revision:	https://reviews.freebsd.org/D52075

Author: Bjoern A. Zeeb

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

@@ -1,7 +1,7 @@
 /*-
  * SPDX-License-Identifier: BSD-2-Clause
  *
- * Copyright (c) 2024 The FreeBSD Foundation
+ * Copyright (c) 2024-2025 The FreeBSD Foundation
  *
  * This software was developed by Björn Zeeb under sponsorship from
  * the FreeBSD Foundation.
@@ -43,4 +43,16 @@
     guard_ ## _n ## _t guard_ ## _n ## _ ## __COUNTER__			\
 	__cleanup(guard_ ## _n ## _destroy) = guard_ ## _n ## _create
 
+#define	DEFINE_FREE(_n, _t, _f)						\
+    static inline void							\
+    __free_ ## _n(void *p)						\
+    {									\
+	_t _T;								\
+									\
+	_T = *(_t *)p;							\
+	_f;								\
+    }
+
+#define	__free(_n)		__cleanup(__free_##_n)
+
 #endif	/* _LINUXKPI_LINUX_CLEANUP_H */

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

@@ -40,8 +40,10 @@
 #include <linux/compat.h>
 #include <linux/types.h>
 #include <linux/gfp.h>
+#include <linux/err.h>
 #include <linux/llist.h>
 #include <linux/overflow.h>
+#include <linux/cleanup.h>
 
 MALLOC_DECLARE(M_KMALLOC);
 
@@ -153,6 +155,8 @@ kfree(const void *ptr)
 	lkpi_kfree(ptr);
 }
 
+DEFINE_FREE(kfree, void *, if (!IS_ERR_OR_NULL(_T)) kfree(_T))
+
 /*
  * Other k*alloc() funtions using the above as underlying allocator.
  */