staging:rtl8192u: Remove unused structure QOS_CTRL_FIELD - Style

The structure QOS_CTRL_FIELD is unused in code so has simply been removed
from source. This is a coding style change and should have no impact
on runtime code execution.

Signed-off-by: John Whitmore <johnfwhitmore@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>