Instead of having the I2C register calculation function spread across
multiple accessor functions, pull it out into a single function which
returns the adjusted register address.
Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>