ELBERT: Add MAX6581 in userspace (#117)

Summary:
ELBERT: Add MAX6581 in userspace

- Add TH4 Diode temp sensor in setup_i2c.sh instead of dts. This allows
  it to retry adding the device if it fails to probe for any reason.

Testing:

Following tests no longer occasionally fail
- test_i2c
- test_sensor_calibration

Pull Request resolved: facebookexternal/openbmc.arista#117

Reviewed By: tao-ren

fbshipit-source-id: 39d1436ef3

meta-facebook/meta-elbert/recipes-utils/openbmc-utils/files/setup_i2c.sh

@@ -59,10 +59,19 @@ hwmon_device_add() {
     fi
 }
 
+# Calibrate TH4 MAX6581
+calibrate_th4_max6581() {
+    i2cset -f -y 4 0x4d 0x4a 0x03
+    i2cset -f -y 4 0x4d 0x4b 0x1f
+    i2cset -f -y 4 0x4d 0x4c 0x03
+}
+
 # Probe FSCD devices first in case one module is taking too
 # long or is in bad shape
 # Supvervisor Inlet
 hwmon_device_add 11 0x4c max6658
+hwmon_device_add 4 0x4d max6581
+calibrate_th4_max6581
 
 # SMBus 0
 # Currently not using I2C TPM