staging: rtl8723bs: remove unused structures

staging: rtl8723bs: remove unused structures

Building this with 'make W=1' produces a couple of warnings:

rtl8723bs/include/ieee80211.h:730:1: warning: alignment 1 of 'struct ieee80211_assoc_request_frame' is less than 2 [-Wpacked-not-aligned]
rtl8723bs/include/ieee80211.h:737:1: warning: alignment 1 of 'struct ieee80211_assoc_response_frame' is less than 2 [-Wpacked-not-aligned]

The warnings are in dead code, so just remove the bits that
are obviously broken like this.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20210204162956.3276523-1-arnd@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>