staging: r8188eu: use ieee80211 define for version check

Use the IEEE80211_FCTL_VERS define to check the version number
of a received frame.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>

drivers/staging/r8188eu/core/rtw_recv.c

@@ -1063,7 +1063,6 @@ static int validate_recv_frame(struct adapter *adapter, struct recv_frame *precv
 	struct rx_pkt_attrib *pattrib = &precv_frame->attrib;
 	u8 *ptr = precv_frame->rx_data;
 	__le16 fc = *(__le16 *)ptr;
-	u8  ver = (unsigned char)(*ptr) & 0x3;
 	struct mlme_ext_priv *pmlmeext = &adapter->mlmeextpriv;
 
 	if (pmlmeext->sitesurvey_res.state == SCAN_PROCESS) {
@@ -1072,8 +1071,7 @@ static int validate_recv_frame(struct adapter *adapter, struct recv_frame *precv
 			pmlmeext->channel_set[ch_set_idx].rx_count++;
 	}
 
-	/* add version chk */
-	if (ver != 0)
+	if ((fc & IEEE80211_FCTL_VERS) != 0)
 		return _FAIL;
 
 	pattrib->to_fr_ds = get_tofr_ds(ptr);