This library function should be in obj-y and not in lib-y. But when we do
that it clashes unpleasantly with the assembly-language implementation in the
ia64 architecture.
Instead of trying to fix it all up, just remove the generic carta_random32 in
the expectation that the recently-made-generic random32() will suffice.
If/when perfmon is migrated to random32, ia64's private carta_random32
implementation can also be removed.