ida: Start new test_ida module

Start transitioning the IDA tests into kernel space.  Framework heavily
cribbed from test_xarray.c.

Signed-off-by: Matthew Wilcox <willy@infradead.org>

tools/testing/radix-tree/test.h

@@ -39,8 +39,7 @@ void multiorder_checks(void);
 void iteration_test(unsigned order, unsigned duration);
 void benchmark(void);
 void idr_checks(void);
-void ida_checks(void);
-void ida_thread_tests(void);
+void ida_tests(void);
 
 struct item *
 item_tag_set(struct radix_tree_root *root, unsigned long index, int tag);