staging: brcm80211: Remove unneeded definitions and structures.

Remove definitions and structures that are no longer needed.  Most of the
remaining ones can probably be replaced with the equivalent ones from
include/linux/ieee80211.h.
Signed-off-by: NHenry Ptasinski <henryp@broadcom.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>