Enable L0D filter without L0I

The -L0_filter option in drmemtrace enables both L0I and L0D caches: https://github.com/DynamoRIO/dynamorio/blob/f4c390b7e70366e4237b27a78a68b9e892f90a1c/clients/drcachesim/common/options.cpp#L165

We want to be able to enable just L0D, without any filtering on instructions.