[media] media: i2c: ADV7604: Rename adv7604 prefixes

It is confusing which parts of the driver are adv7604 specific, adv7611
specific or common for both. This patch renames any adv7604 prefixes (both
for functions and defines) to adv76xx whenever they are common.

Signed-off-by: Pablo Anton <pablo.anton@vodalys-labs.com>
Signed-off-by: Jean-Michel Hautbois <jean-michel.hautbois@vodalys.com>
[hans.verkuil@cisco.com: rebased and renamed ADV76xx_fsc to ADV76XX_FSC]
[hans.verkuil@cisco.com: kept the existing adv7604 driver name]
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>

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