radix tree test suite: allow testing other fan-out values

The defines in regression2.c are already in radix-tree.h and duplicating
them in the test case makes experimenting with other values for the
fan-out harder than necessary.  Allow the user of the radix tree to
decide what the fan-out should be rather than fixing it to 8 for
non-kernel uses.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/tools/testing/radix-tree/linux/kernel.h b/tools/testing/radix-tree/linux/kernel.h
index 76a88f3..31fe2c77 100644
--- a/tools/testing/radix-tree/linux/kernel.h
+++ b/tools/testing/radix-tree/linux/kernel.h
@@ -12,6 +12,8 @@
 #define CONFIG_SHMEM
 #define CONFIG_SWAP
 
+#define RADIX_TREE_MAP_SHIFT	3
+
 #ifndef NULL
 #define NULL	0
 #endif