staging: rtl8723bs: fix issue "Using comparison to true is error prone"

this patch fixes below issue reported by checkpatch

CHECK: Using comparison to true is error prone
+                       if (res == true)
Signed-off-by: Hariprasad Kelam <hariprasad.kelam@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8723bs/os_dep/xmit_linux.c

@@ -231,7 +231,7 @@ int _rtw_xmit_entry(_pkt *pkt, _nic_hdl pnetdev)
 		&& padapter->registrypriv.wifi_spec == 0) {
 		if (pxmitpriv->free_xmitframe_cnt > (NR_XMITFRAME/4)) {
 			res = rtw_mlcst2unicst(padapter, pkt);
-			if (res == true)
+			if (res)
 				goto exit;
 		} else {
 			/* DBG_871X("Stop M2U(%d, %d)! ", pxmitpriv->free_xmitframe_cnt, pxmitpriv->free_xmitbuf_cnt); */