i2c: riic: Use devm_platform_ioremap_resource()

Use the devm_platform_ioremap_resource() helper instead of calling
platform_get_resource() and devm_ioremap_resource() separately.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>