add Enabled properties and remove unused methods nmiEnable

Currently, x86-power-control is using property "Enabled"
to monitor NMI Source. But, NMISource.interface.yaml didn't
have this "Enabled" property and the methods "nmiEnable" seems
unused in current openbmc design, remove it avoid usage confusion.

Signed-off-by: Tim Lee <timlee660101@gmail.com>
Change-Id: I1d7751cfe0de6c919ecd0deaea4a801db4d8b86e
diff --git a/yaml/xyz/openbmc_project/Chassis/Control/NMISource.interface.yaml b/yaml/xyz/openbmc_project/Chassis/Control/NMISource.interface.yaml
index cb1d037..ce302d4 100644
--- a/yaml/xyz/openbmc_project/Chassis/Control/NMISource.interface.yaml
+++ b/yaml/xyz/openbmc_project/Chassis/Control/NMISource.interface.yaml
@@ -1,12 +1,5 @@
 description: >
     An interface for NMI signal source.
-methods:
-    - name: nmiEnable
-      description: >
-          Enables the BMC NMI out event.
-      errors:
-          - xyz.openbmc_project.Chassis.Common.Error.UnsupportedCommand
-          - xyz.openbmc_project.Chassis.Common.Error.IOError
 
 properties:
     - name: BMCSource
@@ -14,6 +7,11 @@
       description: >
           Keeps track of NMI signal source in BMC.
       default: "None"
+    - name: Enabled
+      type: boolean
+      description: >
+          whether the BMC enables NMI event.
+      default: false
 
 enumerations:
     - name: BMCSourceSignal