RDMA/cxgb4: Free debugfs on registration failure

In the Linux kernel, the following vulnerability has been resolved: RDMA/cxgb4: Free debugfs on registration failure c4iw_alloc() creates the per-device debugfs tree (dev->debugfs_root via setup_debugfs()), but it is removed only in c4iw_remove(), not in c4iw_dealloc(). When RDMA device registration fails, the registration worker's err_dealloc_ctx path calls c4iw_dealloc() directly, bypassing c4iw_remove(), so the debugfs dentries leak and outlive the freed c4iw_dev. Move debugfs_remove_recursive() into c4iw_dealloc() so every path that frees ctx->dev also removes its debugfs tree.