Set Witherspoon hwmon target mode

Set the target mode for the MAX31785 fan controller
device to be RPM mode so phosphor-hwmon doesn't also
create an interface for PWM control.

Resolves openbmc/openbmc#2940

Tested: Used this config file with the corresponding
        phosphor-hwmon changes and ensured the correct
        interface was created.

Change-Id: I6a1361e0264dde252b838c6428fae8b921e0d381
Signed-off-by: Matt Spinler <spinler@us.ibm.com>
diff --git a/meta-witherspoon/recipes-phosphor/sensors/phosphor-hwmon%/obmc/hwmon/ahb/apb/i2c@1e78a000/i2c-bus@100/max31785@52.conf b/meta-witherspoon/recipes-phosphor/sensors/phosphor-hwmon%/obmc/hwmon/ahb/apb/i2c@1e78a000/i2c-bus@100/max31785@52.conf
index a4bbe92..0417ea8 100644
--- a/meta-witherspoon/recipes-phosphor/sensors/phosphor-hwmon%/obmc/hwmon/ahb/apb/i2c@1e78a000/i2c-bus@100/max31785@52.conf
+++ b/meta-witherspoon/recipes-phosphor/sensors/phosphor-hwmon%/obmc/hwmon/ahb/apb/i2c@1e78a000/i2c-bus@100/max31785@52.conf
@@ -6,3 +6,4 @@
 LABEL_fan6 = "fan1_1"
 LABEL_fan7 = "fan2_1"
 LABEL_fan8 = "fan3_1"
+TARGET_MODE = "RPM"