rtl8192du: Partially restore 5G performance

The original driver is capable of about 80 Mbps when running netperf
TCP tests. Commit d88f1fa introduced an error that cut the throughput
to about 30 Mbps. These changes improve the results to RX of 46 and TX
of 60 Mbps.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
rtl8192du: Change CamelCase file names to be lower case

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>