mkvmlinuz binary package in Ubuntu Xenial powerpc

 This little program takes a PowerPC Linux kernel as an uncompressed
 ELF image file (usually called vmlinux or such) and adds boot code
 and possibly a ramdisk to create a compressed kernel image that
 can be booted directly from Open Firmware, thus eliminating the
 need for a second-stage bootloader such as yaboot or quik. This is
 especially useful on PowerPC sub-architectures which do not have a
 bootloader at all, but may also come in handy for install kernels,
 netboot systems, and the like.

Source package