i2c: gpio: Add support on ACPI-based system

Add support for the ACPI-based device registration, so that the driver
can be also enabled through ACPI table.

Signed-off-by: Binbin Zhou <zhoubinbin@loongson.cn>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Tested-by: Peibao Liu <liupeibao@loongson.cn>
Signed-off-by: Wolfram Sang <wsa@kernel.org>