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 <[e-mail]>
Reviewed-by: Dan Carpenter <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/staging/rtl8723bs/core/rtw_mlme_ext.c

···
 		/* 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 */
···
 	/* 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 */