i2c: rk3x: Adjust mask/value offset for i2c2 on rv1126

Rockchip RV1126 is using old style i2c controller, the i2c2
bus uses a non-sequential offset in the grf register for the
mask/value bits for this bus.

This patch fixes i2c2 bus on rv1126 SoCs.

Signed-off-by: Tim Lunn <tim@feathertop.org>
Acked-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Andi Shyti <andi.shyti@kernel.org>
Signed-off-by: Wolfram Sang <wsa@kernel.org>