Apparently we don't have an archclean target in our
arch/parisc/Makefile, so files in there never get cleaned out by make
mrproper. This, in turn means that the sizes.h file in
arch/parisc/boot/compressed never gets removed and worse, when you
transition to an O=build/parisc[64] build model it overrides the
generated file. The upshot being my bzImage was building with a SZ_end
that was too small.