Staging: rtl8192u: ieee80211: Convert comment from C99 style to C89 style

This patch fixes the checkpatch.pl error:
ERROR: "Do not use C99 // comments"

Signed-off-by: Hatice ERTURK <haticeerturk27@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>