media: i2c: imx214: Replace register addresses with macros

Define macros for all the known registers used in the register arrays,
and use them to replace the numerical addresses. This improves
readability.

Acked-by: Ricardo Ribalda <ribalda@chromium.org>
Signed-off-by: André Apitzsch <git@apitzsch.eu>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>