V4L/DVB (13528): em28xx: add support for em2800 VC211A card

Adds support to VC211A em2800 card. As this board doesn't have eeprom,
and uses a common set of i2c address, it has no way to add any
autodetection for it.

The patch were tested by me and by Raimundo on his board. Thanks to
those tests, several bugs related to em2800 support were corrected.

for producing the usbsnoop dump, used to get the gpio's and allowing me
to remotelly access his machine and to the needed tests.

Thanks-to: Raimundo Eduvirgnes de Oliveira <eduvirgens@yahoo.com.br>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>