staging:rtl8192u: Rename ShortData - Style

Rename the ShortData member variable to short_data. This clears a
checkpatch issue with CamelCase naming.

This is a coding style change which should not impact runtime
code execution.

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