This conflict is designed into the driver. Linux is simply
recognizing that the BIOS AML is accessing the same resources
and thus automatically dis-allowing the driver to load.
If it is important that you run i2c_piix4,
you can disable ACPI via BIOS SETUP or cmdline "acpi=off".
You will likely lose more by disabling ACPI
than you will by disabling i2c_piix4, but it is technically your choice…