rtw89: ps: fine tune polling interval while changing low power mode

By experiments, it spends ~45/1090~2480us to enter/leave low power mode,
so the old polling interval 1000us can waste time. Use smaller polling
interval depends on experimental results to reduce the time to transition
state.

Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20220503120001.79272-5-pkshih@realtek.com