staging: rtl8192u: fix comments in r819xU_cmdpkt.h

This patch fixes the comments in r819xU_cmdpkt.h by:
* removing any empty or unnecessary comments
* replacing the // comments with /* */ comments
* removing date and author information from comments

This is done to improve code readability and to conform to linux kernel
coding style.

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