[media] siano: use a separate completion for stats

Instead of re-use tune_done also for stats, the better is to use
a different completion.
Also, it was noticed that sometimes, the driver answers with
MSG_SMS_SIGNAL_DETECTED_IND for status request. Fix the code to
also handle those other signal indicators.

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>