tools/include: Add _RET_IP_ and math definitions to kernel.h

commit 5cf67a60 upstream.

Add max_t, min_t and clamp functions, together with _RET_IP_
definition, so they can be used in testing.

Signed-off-by: Karolina Drobnik <karolinadrobnik@gmail.com>
Signed-off-by: Mike Rapoport <rppt@kernel.org>
Link: https://lore.kernel.org/r/230fea382cb1e1659cdd52a55201854d38a0a149.1643796665.git.karolinadrobnik@gmail.com


[tyhicks: Backport around contextual differences due to the lack of v5.16 commit
 d6e6a27d ("tools: Fix math.h breakage"). That commit fixed a commit
 that was merged in v5.16-rc1 and, therefore, doesn't need to go back to
 the stable branches.]
Signed-off-by: Tyler Hicks (Microsoft) <code@tyhicks.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>