phosphor-dbus-interfaces: Add enum value "Pascals"

The `DBus-sensors` package now implements the pressure sensor,
and the `xyz.openbmc_project.Sensor.Value` should provide the
`Pascals` at enum's of "Unit"-property.

End-user-impact: The `xyz.openbmc_project.Sensor.Value.Unit`
                 now represents the 'Pascals' type of pressure
                 sensors values.

Signed-off-by: Bruce Mitchell <bruce.mitchell@linux.vnet.ibm.com>
Change-Id: I926a6aa35e15f1513bd21066f8cda68fbc9a5b69
diff --git a/xyz/openbmc_project/Sensor/Value.interface.yaml b/xyz/openbmc_project/Sensor/Value.interface.yaml
index 1062105..e825c9a 100644
--- a/xyz/openbmc_project/Sensor/Value.interface.yaml
+++ b/xyz/openbmc_project/Sensor/Value.interface.yaml
@@ -11,6 +11,7 @@
       power
       energy
       utilization
+      pressure
 
     Any service implementing Sensor.Value on one or more objects must
     implement org.freedesktop.DBus.ObjectManager on the sensors namespace root.
@@ -45,6 +46,7 @@
           For objects in the energy namespace, Unit must be "Joules".
           For objects in the utilization namespace, Unit must be "Percent"
           For objects in the airflow namespace, Unit must be "CFM"
+          For objects in the pressure namespace, Unit must be "Pascals"
 
 enumerations:
     - name: Unit
@@ -78,3 +80,6 @@
         - name: CFM
           description: >
             To calculate Air Flow in Cubic Feet per Minute
+        - name: Pascals
+          description: >
+            Pressure as pascal.