nimble/ll: Add restriction when enabling periodic advertising

Periodic advertising requires extended advertising to be enabled.
diff --git a/nimble/controller/syscfg.yml b/nimble/controller/syscfg.yml
index 2c7c2cb..b900ba9 100644
--- a/nimble/controller/syscfg.yml
+++ b/nimble/controller/syscfg.yml
@@ -243,6 +243,8 @@
             This option is used to enable/disable support for Periodic
             Advertising Feature.
         value: MYNEWT_VAL(BLE_PERIODIC_ADV)
+        restrictions:
+            - 'BLE_LL_CFG_FEAT_LL_EXT_ADV if 1'
 
     BLE_LL_CFG_FEAT_LL_PERIODIC_ADV_SYNC_CNT:
         description: >