ipamap is missing for rpi4_64

#67 modified `ipamap` to have `linux_ipamap` and `guest_ipamap` in `so3/arch/arm64/virt64/include/mach/ipamap.h` but not in `so3/arch/arm64/rpi4_64/include/mach/ipamap.h`. This lead build fail of SO3 with `rpi4_64_avz_defconfig`.