rtw88: 8723d: 11N chips don't support H2C queue

H2C queue is used to send command to firmware. Since 8723D doesn't support
this queue, this commit check wlan_cpu flag to avoid to set H2C related
registers.

Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Yan-Hsuan Chuang <yhchuang@realtek.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200422034607.28747-6-yhchuang@realtek.com