smb: client: remove pointless sc->recv_io.credits.count rollback

We either reach this code path before we call
new_credits = manage_credits_prior_sending(sc),
which means new_credits is still 0
or the connection is already broken as
smbd_post_send() already called
smbd_disconnect_rdma_connection().

This will also simplify further changes.

Cc: <stable@vger.kernel.org> # 6.18.x
Cc: Steve French <smfrench@gmail.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Long Li <longli@microsoft.com>
Cc: Namjae Jeon <linkinjeon@kernel.org>
Cc: linux-cifs@vger.kernel.org
Cc: samba-technical@lists.samba.org
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: metze-samba

fs/smb/client/smbdirect.c

@@ -1288,9 +1288,6 @@ static int smbd_post_send_iter(struct smbdirect_socket *sc,
 					    DMA_TO_DEVICE);
 	mempool_free(request, sc->send_io.mem.pool);
 
-	/* roll back the granted receive credits */
-	atomic_sub(new_credits, &sc->recv_io.credits.count);
-
 err_alloc:
 	atomic_inc(&sc->send_io.credits.count);
 	wake_up(&sc->send_io.credits.wait_queue);