lantiq: kernel 5.4: debloat kernel config

lantiq: kernel 5.4: debloat kernel config

The etop driver is used by all targets except xrx200.

Remove the UBIFS compression support for zlib and zstd from the xway
subtarget. The hardware is EOL for a long time and it's unlikely to ever
see a board shipped with an UBIFS using these compression methods.

Remove the JFFS2 support. Support for jjfs2 images was dropped years
ago.

It shrinks the compressed kernel up to 130 KByte.

Signed-off-by: Mathias Kresin <dev@kresin.me>