Use a macro to define the cache sizes when cachesize > 1 MB.

This is less typing, and less prone to introducing bugs like we
saw in e02e0e1a, and means we
don't have to do maths when adding new non-power-of-2 updates
like those seen recently.
Signed-off-by: NDave Jones <davej@redhat.com>
LKML-Reference: <20100104144735.GA18390@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>