V4L/DVB (9752): Remove duplicated fields on em28xx_board and em28xx structs

Several fields are duplicated on both structs. Let's just copy em28xx_board instead.

A later cleanup could just copy the fields that are changed, in order to keep em28xx_board
const.

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