[media] dib0700: better document struct init

Instead of using anonymous initialization for dib0896 structs,
identify each field by name. That helps to understand what's
being initialized.

No functional changes.

Acked-By: Patrick Boettcher <pboettcher@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>