wifi: rtw89: fix disabling concurrent mode TX hang issue

When disabling concurrent mode and switching to a single interface, the
TX might stuck. The reason is TBTT prohibit area circuit still enable
to block TX. To disable tbtt prohibit area circuit need to delay 2ms to
make it effective. However, we only delay 2us in original code. So we
fix it.

Signed-off-by: Chih-Kang Chang <gary.chang@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://msgid.link/20240119081501.25223-9-pkshih@realtek.com