Staging: rtl8723bs: prevent buffer overflow in update_sta_support_rate()

Staging: rtl8723bs: prevent buffer overflow in update_sta_support_rate()

The "ie_len" variable is in the 0-255 range and it comes from the
network.  If it's over NDIS_802_11_LENGTH_RATES_EX (16) then that will
lead to memory corruption.

Fixes: 84ed90a855bc ("staging: Add rtl8723bs sdio wifi driver")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20200603101958.GA1845750@mwanda
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>