[media] siano: Convert it to report DVBv5 stats

While this frontend provides a nice set of statistics, the
way it is currently reported to userspace is poor. Worse than
that, instead of using quality indicators that range from 0 to 65535,
as expected by userspace, most indicators range from 0 to 100.
Improve it by using DVBv5 statistics API. The legacy indicators
are still reported using the very same old way, but they're now
using a proper range (0 to 65535 for quality indicadors; 0.1 dB
for SNR).

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