radix tree test suite: Fix build

- Add an empty linux/compiler_types.h (now being included by kconfig.h)
 - Add __GFP_ZERO
 - Add kzalloc
 - Test __GFP_DIRECT_RECLAIM instead of __GFP_NOWARN

Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>

tools/testing/radix-tree/linux/gfp.h

@@ -11,6 +11,7 @@
 #define __GFP_IO		0x40u
 #define __GFP_FS		0x80u
 #define __GFP_NOWARN		0x200u
+#define __GFP_ZERO		0x8000u
 #define __GFP_ATOMIC		0x80000u
 #define __GFP_ACCOUNT		0x100000u
 #define __GFP_DIRECT_RECLAIM	0x400000u

tools/testing/radix-tree/linux/slab.h

@@ -3,6 +3,7 @@
 #define SLAB_H
 
 #include <linux/types.h>
+#include <linux/gfp.h>
 
 #define SLAB_HWCACHE_ALIGN 1
 #define SLAB_PANIC 2
@@ -11,6 +12,11 @@
 void *kmalloc(size_t size, gfp_t);
 void kfree(void *);
 
+static inline void *kzalloc(size_t size, gfp_t gfp)
+{
+        return kmalloc(size, gfp | __GFP_ZERO);
+}
+
 void *kmem_cache_alloc(struct kmem_cache *cachep, int flags);
 void kmem_cache_free(struct kmem_cache *cachep, void *objp);