kbuild: fix for updated LZ4 tool with the new streaming format

LZ4 has been updated with LZ4 Streaming Format specification(v1.3).
lz4demo is replaced by lz4c. lz4c supports both the new streaming and
legacy format with -l option.

This patch makes use of lz4c to support legacy format which is
used for LZ4 De/compression in the linux kernel.

Link: https://code.google.com/p/lz4/source/checkout

https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/commit/?id=b078915464637215645a2dcf388a0402986f4a41
config: fix: warning: unexpected data