Plumb up Makefile arguments for the already supported formats in the kbuild
system: lz4, bzip2, lzma, and lzo.

Note that just as with Image.gz, these images are not self-decompressing and
the booting firmware still needs to handle decompression before launching the
kernel image.
Signed-off-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Will Deacon <will.deacon@arm.com>