staging: rtl8723bs: replace FIELD_OFFSET usage with offsetof in rtw_mlme_ext.c

Replace usage of the custom FIELD_OFFSET macro with the standard
offsetof() macro in rtw_mlme_ext.c. This improves code readability
and uses the kernel's standard mechanism.

Signed-off-by: Navaneeth K <knavaneeth786@gmail.com>
Reviewed-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://patch.msgid.link/20251125112059.16913-5-knavaneeth786@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: cyberkunju

drivers/staging/rtl8723bs/core/rtw_mlme_ext.c

@@ -5244,7 +5244,7 @@ u8 createbss_hdl(struct adapter *padapter, u8 *pbuf)
 		/* clear CAM */
 		flush_all_cam_entry(padapter);
 
-		memcpy(pnetwork, pbuf, FIELD_OFFSET(struct wlan_bssid_ex, ie_length));
+		memcpy(pnetwork, pbuf, offsetof(struct wlan_bssid_ex, ie_length));
 		pnetwork->ie_length = ((struct wlan_bssid_ex *)pbuf)->ie_length;
 
 		if (pnetwork->ie_length > MAX_IE_SZ)/* Check pbuf->ie_length */
@@ -5308,7 +5308,7 @@ u8 join_cmd_hdl(struct adapter *padapter, u8 *pbuf)
 	/* pmlmeinfo->assoc_AP_vendor = HT_IOT_PEER_MAX; */
 	pmlmeinfo->VHT_enable = 0;
 
-	memcpy(pnetwork, pbuf, FIELD_OFFSET(struct wlan_bssid_ex, ie_length));
+	memcpy(pnetwork, pbuf, offsetof(struct wlan_bssid_ex, ie_length));
 	pnetwork->ie_length = ((struct wlan_bssid_ex *)pbuf)->ie_length;
 
 	if (pnetwork->ie_length > MAX_IE_SZ)/* Check pbuf->ie_length */