Xc5000 tuning attempts shouldn't return zero in the case where the firmware
did not load successfully.

Thanks to Michael Krufky for pointing out this issue.

Cc: Michael Krufky <mkrufky@kernellabs.com>
Signed-off-by: Devin Heitmueller <dheitmueller@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>