staging:rtl8192u: Remove unused enumerated type QOS_ELE_SUBTYPE - Style

The enumerated type QOS_ELE_SUBTYPE is unused in code so has been removed
from code. This is a coding style change which should have not impact on
runtime code execution.

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