libertas_tf: move the banner to a more appropriate place

Also, turn it to a dev_info() to make checkpatch.pl happy.

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Reviewed-by: Steve deRosier <derosier@cal-sierra.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>