wifi: ath11k: document HAL_RX_BUF_RBM_SW4_BM

Commit 7636c9a6 ("wifi: ath11k: Add multi TX ring support for WCN6750")
added HAL_RX_BUF_RBM_SW4_BM to enum hal_rx_buf_return_buf_manager. However,
as flagged by the kernel-doc script, the documentation was not updated:

drivers/net/wireless/ath/ath11k/hal.h:689: warning: Enum value 'HAL_RX_BUF_RBM_SW4_BM' not described in enum 'hal_rx_buf_return_buf_manager'

So update the documentation. No functional changes, compile tested only.
Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://msgid.link/20240111-document-hal_rx_buf_rbm_sw4_bm-v1-1-ad277e8ab3cc@quicinc.com

drivers/net/wireless/ath/ath11k/hal.h

 /* SPDX-License-Identifier: BSD-3-Clause-Clear */
 /*
  * Copyright (c) 2018-2019 The Linux Foundation. All rights reserved.
- * Copyright (c) 2021-2022 Qualcomm Innovation Center, Inc. All rights reserved.
+ * Copyright (c) 2021-2022, 2024 Qualcomm Innovation Center, Inc. All rights reserved.
  */
 
 #ifndef ATH11K_HAL_H
@@ -674,6 +674,7 @@ struct hal_srng_config {
  * @HAL_RX_BUF_RBM_SW1_BM: For Tx completion -- returned to host
  * @HAL_RX_BUF_RBM_SW2_BM: For Tx completion -- returned to host
  * @HAL_RX_BUF_RBM_SW3_BM: For Rx release -- returned to host
+ * @HAL_RX_BUF_RBM_SW4_BM: For Tx completion -- returned to host
  */
 
 enum hal_rx_buf_return_buf_manager {