rtw88: restore DACK results to save time

DACK is done right after the hardware has been turned on, which
means it will be done every time we leave the IDLE state.
But it takes ~2 seconds to finish DACK.

We can back up the results and restore them. And it only takes a few
milliseconds to restore the results to the hardware, saving a lot of
time.

Signed-off-by: Yan-Hsuan Chuang <yhchuang@realtek.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>