media: friio-fe: get rid of set_property()

This callback is not actually doing anything but making it to
return an error depending on the DTV frontend command. Well,
that could break userspace for no good reason, and, if needed,
should be implemented, instead, at set_frontend() callback.

So, get rid of it.

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