tools/include: Add cache.h stub

Add a dummy version of the cache header.

Signed-off-by: Karolina Drobnik <karolinadrobnik@gmail.com>
Signed-off-by: Mike Rapoport <rppt@kernel.org>
Link: https://lore.kernel.org/r/5e02865094aaf56dd30772722799e53f4130ebc8.1643796665.git.karolinadrobnik@gmail.com