staging: rtl8192u: fix space after ( in r819xU_cmdpkt.h

This patch removes prohibited space after ( in r819xU_cmdpkt.h according to
the linux kernel coding style convention.

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