staging:rtl8192u: Remove unused structure WMM_TSPEC - Style

Remove the structure WMM_TSPEC as it is unused. This change is a coding
style change and should not impact runtime code execution.

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