[media] fc2580: fix tuning failure on 32-bit arch

[media] fc2580: fix tuning failure on 32-bit arch

There was some frequency calculation overflows which caused tuning
failure on 32-bit architecture. Use 64-bit numbers where needed in
order to avoid calculation overflows.

Thanks for the Finnish person, who asked remain anonymous, reporting,
testing and suggesting the fix.

Cc: <[email protected]>
Signed-off-by: Antti Palosaari <[email protected]>
Signed-off-by: Mauro Carvalho Chehab <[email protected]>