[media] dib0700: avoid the risk of forgetting to add the adapter's size

For every frontend entry, we need to add the adapter's size. There
are already two patches fixing it. So, it doesn't seem trivial to
keep it there at the right place.

Also, currently, the indentation is wrong on all places.

So, it seems that keeping it right is not too trivial.

Better to use a macro that would do it for us, at least while
this is not converted to dvb-usb-v2.

Compile-tested only.

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