staging:rtl8192u: Rename member variable Timer - Style

Rename the member variable Timer to all lowercase to clear the
checkpatch issue with CamelCase naming.

This change is purely a coding style change which 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>