wifi: rtlwifi: Remove unused structs and avoid multiple -Wfamnae warnings

Wflex-array-member-not-at-end is coming in GCC-14, and we are getting
ready to enable it globally.

So, remove unused structs and fix the following
-Wflex-array-member-not-at-end warnings:

drivers/net/wireless/realtek/rtlwifi/btcoexist/../wifi.h:1063:30: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
drivers/net/wireless/realtek/rtlwifi/rtl8188ee/../wifi.h:1063:30: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
drivers/net/wireless/realtek/rtlwifi/rtl8192c/../wifi.h:1063:30: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
drivers/net/wireless/realtek/rtlwifi/rtl8192ce/../wifi.h:1063:30: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
drivers/net/wireless/realtek/rtlwifi/rtl8192cu/../wifi.h:1063:30: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
drivers/net/wireless/realtek/rtlwifi/rtl8192de/../wifi.h:1063:30: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
drivers/net/wireless/realtek/rtlwifi/rtl8192ee/../wifi.h:1063:30: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
drivers/net/wireless/realtek/rtlwifi/rtl8192se/../wifi.h:1063:30: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
drivers/net/wireless/realtek/rtlwifi/rtl8723ae/../wifi.h:1063:30: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
drivers/net/wireless/realtek/rtlwifi/rtl8723be/../wifi.h:1063:30: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
drivers/net/wireless/realtek/rtlwifi/rtl8723com/../wifi.h:1063:30: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
drivers/net/wireless/realtek/rtlwifi/rtl8821ae/../wifi.h:1063:30: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
drivers/net/wireless/realtek/rtlwifi/wifi.h:1063:30: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://msgid.link/ZjLFIa31BGPVCGh1@neat