staging: refresh TODO for rtl8723au

People should not waste time and energy working on this staging driver.
A replacement(rtl8xxxu) using the kernel wireless stack already was merged
in the 4.3 kernel.

Cc: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Kalle Valo <kvalo@codeaurora.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Xose Vazquez Perez <xose.vazquez@gmail.com>
Acked-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8723au/TODO

@@ -9,5 +9,8 @@ TODO:
 - merge Realtek's bugfixes and new features into the driver
 - switch to use MAC80211
 
+A mac80211 driver for this hardware already was integrated at
+drivers/net/wireless/realtek/rtl8xxxu/
+
 Please send any patches to Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
 Jes Sorensen <Jes.Sorensen@redhat.com>, and Larry Finger <Larry.Finger@lwfinger.net>.