tools: fix userspace compilation with new test_xarray changes

tools: fix userspace compilation with new test_xarray changes

Patch series "test_xarray: couple of fixes for v6-9-rc6", v2.

Here are a couple of fixes which should be merged into the queue for
v6.9-rc6.  The first one was reported by Liam, after fixing that I noticed
an issue with a test, and a fix for that is in the second patch.

This patch (of 2):

Liam reported that compiling the test_xarray on userspace was broken.  I
was not even aware that was possible but you can via and you can run these
tests in userspace with:

make -C tools/testing/radix-tree
./tools/testing/radix-tree/xarray

Add the two helpers we need to fix compilation.  We don't need a userspace
schedule() so just make it do nothing.

Link: https://lkml.kernel.org/r/20240423192221.301095-1-mcgrof@kernel.org
Link: https://lkml.kernel.org/r/20240423192221.301095-2-mcgrof@kernel.org
Fixes: a60cc288a1a2 ("test_xarray: add tests for advanced multi-index use")
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Reported-by: "Liam R. Howlett" <Liam.Howlett@oracle.com>
Cc: Daniel Gomez <da.gomez@samsung.com>
Cc: Darrick J. Wong <djwong@kernel.org>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Pankaj Raghav <p.raghav@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>