V4L/DVB (5255): Fix cx25840 firmware loading.

Due to changes in the i2c handling in 2.6.20 this cx25840 bug surfaced,
causing the firmware load to fail for the ivtv driver. The correct
sequence is to first attach the i2c client, then use the client's
device to load the firmware.
Acked-by: Mike Isely <isely@pobox.com>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>