staging: rtl8192u: add parenthesis around complex macros in r819xU_HTType.h

This patch fixes the following checkpatch error:
ERROR: Macros with complex values should be enclosed in parenthesis

Signed-off-by: Xenia Ragiadakou <burzalodowa@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>