Although the newest firmware for the RTL8192SU, which is found in vendor
driver rtl8188C_8192C_8192D_usb_linux_v3.4.2_3727.20120404, works with most
devices, it causes drops of the wireless connection for the ASUS WL-167G V3
(USB ID 0b05:1791), the D-Link DWA131 (07d1:3303), and probably others.
Tests show that the firmware from vendor driver
rtl8712_8188_8191_8192SU_usb_linux_v7_0.20100831 works better.

This commerts reverts to that older firmware.
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>