L3 cache is not defined by Book-E, so is platform specific. Since it was already moved for e500-based devices into mpc85xx in r292903, just eliminate it altogether. Any device that supports L3 cache should have its own platform means to enable it.
skeleton (maybe we should kobj-tize this one day). Note the PPC4xx bit is not connected to the build yet. Obtained from: AppliedMicro, Semihalf.