nimble/host: Convert BLE_GAP_MAX_UPDATE_ENTRIES from define to syscfg.

Previously, BLE_GAP_MAX_UPDATE_ENTRIES was a define in ble_gap.c. Now it's a syscfg in nimble/host/syscfg.yml. There are cases where this value needs to be increased to support multiple simultaneous connections.

nimble/host/src/ble_gap.c

@@ -87,8 +87,6 @@
 
 #define BLE_GAP_UPDATE_TIMEOUT_MS               30000 /* ms */
 
-#define BLE_GAP_MAX_UPDATE_ENTRIES      1
-
 static const struct ble_gap_conn_params ble_gap_conn_params_dflt = {
     .scan_itvl = 0x0010,
     .scan_window = 0x0010,
@@ -188,7 +186,7 @@ struct ble_gap_snapshot {
 static SLIST_HEAD(ble_gap_hook_list, ble_gap_event_listener) ble_gap_event_listener_list;
 
 static os_membuf_t ble_gap_update_entry_mem[
-                        OS_MEMPOOL_SIZE(BLE_GAP_MAX_UPDATE_ENTRIES,
+                        OS_MEMPOOL_SIZE(MYNEWT_VAL(BLE_GAP_MAX_UPDATE_ENTRIES),
                                         sizeof (struct ble_gap_update_entry))];
 static struct os_mempool ble_gap_update_entry_pool;
 static struct ble_gap_update_entry_list ble_gap_update_entries;
@@ -4747,7 +4745,7 @@ ble_gap_init(void)
     SLIST_INIT(&ble_gap_event_listener_list);
 
     rc = os_mempool_init(&ble_gap_update_entry_pool,
-                         BLE_GAP_MAX_UPDATE_ENTRIES,
+                         MYNEWT_VAL(BLE_GAP_MAX_UPDATE_ENTRIES),
                          sizeof (struct ble_gap_update_entry),
                          ble_gap_update_entry_mem,
                          "ble_gap_update");

nimble/host/syscfg.yml

@@ -171,6 +171,12 @@ syscfg.defs:
             for debugging.
         value: 0
 
+    # GAP options.
+    BLE_GAP_MAX_UPDATE_ENTRIES:
+        description: >
+            The maximum number of GAP update entries. (0/1)
+        value: 1
+
     # Supported GATT procedures.  By default:
     #     o Notify and indicate are enabled;
     #     o All other procedures are enabled for centrals.