wifi: cfg80211: fix certs build to not depend on file order

The file for the new certificate (Chen-Yu Tsai's) didn't
end with a comma, so depending on the file order in the
build rule, we'd end up with invalid C when concatenating
the (now two) certificates. Fix that.

Cc: stable@vger.kernel.org
Reported-by: Biju Das <biju.das.jz@bp.renesas.com>
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Fixes: fb768d3b

 ("wifi: cfg80211: Add my certificate")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>