iio: am2315: Remove acpi_device_id table

With CONFIG_ACPI=n and -Werror, 0-day reports:

drivers/iio/humidity/am2315.c:259:36: error:
	'am2315_acpi_id' defined but not used

According to Andy Shevchenko, the ACPI ID used in this driver is fake
and does not really exist. Remove it and with it ACPI support from
the driver.

Note that, if an explicit of_device_id table is added to the driver
it could support the PRP0001 based ACPI approach.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>