Led.Physical: Wrap yaml reserved words within single quote

This interface definition file has ENUM with values Off and On.
This resulted in generated code creating the ENUM with values False and True
instead of Off and On. This is specific to pyyaml parser.

Change-Id: Id824ca1d594c533593264a6dd1121d698e0787dd
Signed-off-by: Vishwanatha Subbanna <vishwa@linux.vnet.ibm.com>
diff --git a/xyz/openbmc_project/Led/Physical.interface.yaml b/xyz/openbmc_project/Led/Physical.interface.yaml
index d0ca460..c0ca00e 100644
--- a/xyz/openbmc_project/Led/Physical.interface.yaml
+++ b/xyz/openbmc_project/Led/Physical.interface.yaml
@@ -4,7 +4,7 @@
 properties:
     - name: State
       type: enum[self.Action]
-      default: Off
+      default: 'Off'
       description: >
         Current State of the LED.
 
@@ -25,13 +25,13 @@
       description: >
           Possible states a LED can be in.
       values:
-        - name: Off
+        - name: 'Off'
           description: >
             LED is in OFF state
-        - name: On
+        - name: 'On'
           description: >
             LED is in solid ON state
-        - name: Blink
+        - name: 'Blink'
           description: >
             LED is blinking