kernel: Fix kmod-lib-lz4 packaging

kernel: Fix kmod-lib-lz4 packaging

The kernel provides two variants of the lz4 compression a normal version
and a high compression mode version. The old kmod-lib-lz4 package
contained the normal version plus one part of the lz4hc version. There
was already code which selected the kmod-lib-lz4hc package which did
not exists.

I split this into 3 packages. kmod-lib-lz4 and kmod-lib-lz4hc for the
normal the and high compression algorithm which contain the specific
code and the kmod-lib-lz4-decompress which contains the common
decompressor.

New we are also packaging lz4hc.ko

Link: https://github.com/openwrt/openwrt/pull/15833
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
(cherry picked from commit fac507606d75eec04762013582273468eea7ed92)
Link: https://github.com/openwrt/openwrt/pull/15898
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>