add config for number of pending adv sets starting

Author: paul-szczepanek-arm

connectivity/FEATURE_BLE/mbed_lib.json

@@ -108,6 +108,11 @@
             "value": 16,
             "macro_name": "BLE_GAP_HOST_PRIVACY_RESOLVED_CACHE_SIZE"
         },
+        "ble-gap-host-max-advertising-start-commands": {
+            "help": "There can only be one outstanding advertising set command sent to the controller. This determines how many advertising set start commands can be queued on the host. Must be between 1 and BLE_GAP_MAX_ADVERTISING_SETS.",
+            "value": 4,
+            "macro_name": "BLE_GAP_HOST_MAX_OUTSTANDING_ADVERTISING_START_COMMANDS"
+        },
 
         "ble-passkey-display-reversed-digits-deprecation": {
           "help": "This option is part of the deprecation process. Set this to false to remove the deprecation notice. When set to true, the digits in the SecurityManager passkeyDiplay event are reversed. When set to false the digits are in the correct order.",