hwmon: (emc1403) Make all hyst attributes except for temp1_crit_hyst read-only

All chips in this chip series only support a single hysteresis value. Having
multiple writable hysteresis attributes is therefore confusing, since a single
write affects all hysteresis temperatures. Make all but one (temp1_crit_hyst)
read-only.

Reviewed-by: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>