drv/bluetooth_btstack: only set AD params once when broadcasting

When broadcasting, the advertising parameters dont' change, so we only
need to set them once when we start broadcasting. This is done by
moving the code inside the if statement along with the enable function.

lib/pbio/drv/bluetooth/bluetooth_btstack.c

@@ -748,9 +748,6 @@ static PT_THREAD(start_broadcasting_task(struct pt *pt, pbio_task_t *task)) {
         PT_EXIT(pt);
     }
 
-    bd_addr_t null_addr = { };
-    gap_advertisements_set_params(0xA0, 0xA0, ADV_NONCONN_IND, 0, null_addr, 0x7, 0);
-
     // have to keep copy of data here since BTStack doesn't copy
     static uint8_t static_data[LE_ADVERTISING_DATA_SIZE];
     memcpy(static_data, value->data, value->size);
@@ -758,6 +755,8 @@ static PT_THREAD(start_broadcasting_task(struct pt *pt, pbio_task_t *task)) {
     gap_advertisements_set_data(value->size, static_data);
 
     if (!is_broadcasting) {
+        bd_addr_t null_addr = { };
+        gap_advertisements_set_params(0xA0, 0xA0, ADV_NONCONN_IND, 0, null_addr, 0x7, 0);
         gap_advertisements_enable(true);
         is_broadcasting = true;
     }