Add airflow sensor support in phosphor-virtual-sensor

TESTED : Built Facebook YosemiteV2 images and loaded on the target hardware.
Verified the dbus objects created for airflow sensor under virtual-sensor.

Signed-off-by: Kumar Thangavel <thangavel.k@hcl.com>
Change-Id: I85cbce561785622d08ea5afcfbe06f2ba34d74f8
diff --git a/virtualSensor.cpp b/virtualSensor.cpp
index b74f0d3..e136db1 100644
--- a/virtualSensor.cpp
+++ b/virtualSensor.cpp
@@ -299,7 +299,8 @@
     {"current", ValueIface::Unit::Amperes},
     {"power", ValueIface::Unit::Watts},
     {"energy", ValueIface::Unit::Joules},
-    {"utilization", ValueIface::Unit::Percent}};
+    {"utilization", ValueIface::Unit::Percent},
+    {"airflow", ValueIface::Unit::CFM}};
 
 void VirtualSensors::createVirtualSensors()
 {