microbit: Populate 'bonds' field in whitelist entry

Update to populate a recently introduced 'bonds' field in the whitelist_t
structure. This field records the number of IRKs present in the table, which
correlates to the number of bonds.

source/nRF5xSecurityManager.h

@@ -74,9 +74,12 @@ public:
         ble_error_t error = createWhitelistFromBondTable(whitelistFromBondTable);
         if (error != BLE_ERROR_NONE) {
             addresses.size = 0;
+            addresses.bonds = 0;
             return error;
         }
 
+        addresses.bonds = whitelistFromBondTable.irk_count;
+
         /* Put all the addresses in the structure */
         for (i = 0; i < whitelistFromBondTable.addr_count; ++i) {
             if (i >= addresses.capacity) {