Add MaxValue and MinValue interface to Sensors

To be able to correctly tell an error has occurred, as
well as to be able to dynamically create sensor scaling
factors the MaxValue and MinValue interface need to be added.
This commit adds these to the interface.

Change-Id: I8f0abfa3446350329c38210beb540faddc0a65a0
Signed-off-by: James Feist <james.feist@linux.intel.com>
diff --git a/xyz/openbmc_project/Sensor/Value.interface.yaml b/xyz/openbmc_project/Sensor/Value.interface.yaml
index daa7f24..5e1b345 100644
--- a/xyz/openbmc_project/Sensor/Value.interface.yaml
+++ b/xyz/openbmc_project/Sensor/Value.interface.yaml
@@ -21,6 +21,14 @@
       type: int64
       description: >
           The sensor reading.
+    - name: MaxValue
+      type: int64
+      description: >
+          The Maximum supported sensor reading.
+    - name: MinValue
+      type: int64
+      description: >
+          The Minimum supported sensor reading.
     - name: Unit
       type: enum[self.Unit]
       description: >