i2c: riic: Simplify reset handling

Read reset phandle as optional instead of exclusive so that all the DT's
passing the reset phandle can be used to assert/deassert the reset line.
With this change we don't have to differentiate the RZ/G2L SoC.

With the above changes we no longer need the "renesas,riic-r9a07g044"
compatible string, so drop it from riic_i2c_dt_ids[]. No changes are
required to the r9a07g044.dtsi as we already have "renesas,riic-rz" as a
fallback compatible string.

While at it, check the return code of reset_control_deassert() as it might
fail and also add a devres action to assert the reset line.

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