iio: xilinx-ams: Fix AMS_ALARM_THR_DIRECT_MASK

AMS_ALARM_THR_DIRECT_MASK should be bit 0, not bit 1. This would cause
hysteresis to be enabled with a lower threshold of -28C. The temperature
alarm would never deassert even if the temperature dropped below the
upper threshold.

Fixes: d5c70627 ("iio: adc: Add Xilinx AMS driver")
Signed-off-by: Sean Anderson <sean.anderson@linux.dev>
Reviewed-by: O'Griofa, Conall <conall.ogriofa@amd.com>
Tested-by: Erim, Salih <Salih.Erim@amd.com>
Acked-by: Erim, Salih <Salih.Erim@amd.com>
Link: https://patch.msgid.link/20250715003058.2035656-1-sean.anderson@linux.dev


Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>