Recent changes to BuildBot config moved the kmods to a dedicated
directory and dropped them from the packages dir. This was needed as
both OPKG and APK gets confused if both entry are present.
To fix this, unconditionally append the kmod feed line if
CONFIG_BUILDBOT is enabled.
Fixes: #17146
Link: https://github.com/openwrt/openwrt/pull/17151
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>