Instead of failing to identify a compressed image with a decompressor
that we don't have compiled in, identify it and fail with a
comprehensible panic message.
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Centralize the compression format detection to a common routine in the
lib directory, and use it for both initramfs and initrd.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>