staging: rtl8723au: Remove unnecessary null test before kfree

Fix checkpatch warning:
WARNING: kfree(NULL) is safe this check is probably not required

Cc: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Jes Sorensen <Jes.Sorensen@redhat.com>
Cc: linux-wireless@vger.kernel.org
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8723au/core/rtw_cmd.c

@@ -515,9 +515,7 @@ int rtw_joinbss_cmd23a(struct rtw_adapter *padapter,
 
 	psecnetwork = &psecuritypriv->sec_bss;
 	if (!psecnetwork) {
-		if (pcmd)
-			kfree(pcmd);
-
+		kfree(pcmd);
 		res = _FAIL;
 
 		RT_TRACE(_module_rtl871x_cmd_c_, _drv_err_,