Staging: rtl8192su/ieee80211: ieee80211.h cleanups

* remove unused / duplicated definitions
* remove unused / used only once typedefs
* fix comments, remove useless ones
* convert defines to enums where appropriate
* use __func__ instead of __FUNCTION__
* make some minor coding style fixes
* misc cleanups

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>