iio:potentiometer:max5481: Drop invalid ACPI binding.

Given that an ACPI binding must start with 3 or 4 capitals,
this cannot represent a valid binding.

It seems unlikely anything out there is using it.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Maury Anderson <maury.anderson@rockwellcollins.com>
Cc: Matthew Weber <matthew.weber@rockwellcollins.com>
Cc: Slawomir Stepien <sst@poczta.fm>
Link: https://lore.kernel.org/r/20200910173242.621168-6-jic23@kernel.org