wifi: rtlwifi: remove unused dualmac control leftovers

Remove 'struct rtl_dualmac_easy_concurrent_ctl' of 'struct rtl_priv'
and related code in '_rtl_pci_tx_chk_waitq()'.

Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
Acked-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20230602065940.149198-2-dmantipov@yandex.ru