wifi: rtw89: Refine active scan behavior in 6 GHz

The interval between sending each probe request is regulated. Before
this patch, some packets are not sent out properly because of our HW
limit. Extend the 6 GHz channel dwell time to cope with this.

Signed-off-by: Po-Hao Huang <phhuang@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20231129070046.18443-3-pkshih@realtek.com