wifi: rtw89: fix firmware scan delay unit for WiFi 6 chips

The scan delay unit of firmware command for WiFi 6 chips is
microsecond, but is wrong set now and lead to abnormal work
for net-detect. Correct the unit to avoid the error.

Fixes: e99dd80c ("wifi: rtw89: wow: add delay option for net-detect")
Signed-off-by: Chin-Yen Lee <timlee@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/20250513125203.6858-1-pkshih@realtek.com