media: i2c: adv748x: Simplify regmap configuration

The ADV748x has identical map configurations for each register map. The
duplication of each map can be simplified using a helper macro such that
each map is represented on a single line.

Define ADV748X_REGMAP_CONF for this purpose use it to create the tables.

Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>