nimble: Add BLE_EXT_ADV MYNEWT_VAL

This flag is used to enable extended advertising in host and controller
(due to dependecies)

X-Original-Commit: 1879eaeb023256a1e81714cfe94b06728e36afc8

nimble/controller/syscfg.yml

@@ -240,7 +240,10 @@ syscfg.defs:
             This option is used to enable/disable support for Extended
             Advertising Feature. That means extended scanner, advertiser
             and connect.
-        value: 0
+        value: MYNEWT_VAL_BLE_EXT_ADV
+        restrictions:
+            - 'BLE_EXT_ADV if 1'
+            - '!BLE_EXT_ADV if 0'
 
     BLE_PUBLIC_DEV_ADDR:
         description: >

nimble/syscfg.yml

@@ -51,3 +51,7 @@ syscfg.defs:
             advertising instances is this number plus 1 (assuming the device
             supports advertising).
         value: 0
+    BLE_EXT_ADV:
+        description: >
+            This enables extended advertising feature.
+        value: 0