Revert "iio: temperature: maxim_thermocouple: add MAX31856 part"

This reverts commit 535fba29.

Seems the submitter (er me, hang head in shame) didn't look at the datasheet
enough to see that the registers are quite different.

This needs to be reverted because a) would never work b) to open it  be added
to a Maxim RTDs (Resistance Temperature Detectors) under development by author
Signed-off-by: NMatt Ranostay <matt.ranostay@konsulko.com>
Signed-off-by: NJonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/temperature/maxim_thermocouple.c

@@ -258,7 +258,6 @@ static int maxim_thermocouple_remove(struct spi_device *spi)
 static const struct spi_device_id maxim_thermocouple_id[] = {
 	{"max6675", MAX6675},
 	{"max31855", MAX31855},
-	{"max31856", MAX31855},
 	{},
 };
 MODULE_DEVICE_TABLE(spi, maxim_thermocouple_id);