i2c: riic: Introduce helper functions for I2C read/write operations

i2c: riic: Introduce helper functions for I2C read/write operations

Introduce helper functions for performing I2C read and write operations
in the RIIC driver.

These helper functions lay the groundwork for adding support for the
RZ/V2H SoC. This is essential because the register offsets for the RZ/V2H
SoC differ from those of the RZ/A SoC. By abstracting the read and write
operations, we can seamlessly adapt the driver to support different SoC
variants without extensive modifications.

This patch is part of the preparation process for integrating support for
the RZ/V2H SoC into the RIIC driver.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>