drivers/sensor: si7006: Remove unused struct device field

Use was removed but the field itself wasn't deleted.

Signed-off-by: Trent Piepho <[email protected]>

Author: xyzzy42

drivers/sensor/silabs/si7006/si7006.c

@@ -22,7 +22,6 @@
 LOG_MODULE_REGISTER(si7006, CONFIG_SENSOR_LOG_LEVEL);
 
 struct si7006_data {
-	const struct device *i2c_dev;
 	uint16_t temperature;
 	uint16_t humidity;
 };