mtd-utils: remove lzo build dependency

The build option `--withouth-lzo` is added in the Makefile which makes
the existence of lzo obsolete. To remove the lzo package from
openwrt.git entirely, remove the legacy dependency.

Signed-off-by: Rosen Penev <rosenp@gmail.com>
[improved commit message]
Signed-off-by: Paul Spooren <mail@aparcar.org>