build: Unconditionally append kmod feed for BuildBot

build: Unconditionally append kmod feed for BuildBot

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
(cherry picked from commit 53ee2e8c0339c1d7ace47b8cf390147b86ea8d1d)
[ fix conflict error for missing APK support ]
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>