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: d5c70627a794 ("iio: adc: Add Xilinx AMS driver")
Signed-off-by: Sean Anderson <[e-mail]>
Reviewed-by: O'Griofa, Conall <[e-mail]>
Tested-by: Erim, Salih <[e-mail]>
Acked-by: Erim, Salih <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Cc: <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/adc/xilinx-ams.c

···
 #define AMS_ALARM_THRESHOLD_OFF_10	0x10
 #define AMS_ALARM_THRESHOLD_OFF_20	0x20
 
-#define AMS_ALARM_THR_DIRECT_MASK	BIT(1)
+#define AMS_ALARM_THR_DIRECT_MASK	BIT(0)
 #define AMS_ALARM_THR_MIN		0x0000
 #define AMS_ALARM_THR_MAX		(BIT(16) - 1)