radix tree test suite: Remove ARRAY_SIZE

This is now defined in tools/include/linux/kernel.h, so our
definition generates a warning.
Signed-off-by: NMatthew Wilcox <mawilcox@microsoft.com>

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

@@ -17,6 +17,4 @@
 #define pr_debug printk
 #define pr_cont printk
 
-#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))
-
 #endif /* _KERNEL_H */