[media] r820t: better report signal strength

If signal is zero, shows it as a zero, not as 0xff.

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Tested-by: Antti Palosaari <crope@iki.fi>
This commit is contained in:
Mauro Carvalho Chehab 2013-04-10 09:04:03 -03:00
commit 75c1819e5e