scsi: ufs: core: Fix abnormal scale up after last cmd finish

scsi: ufs: core: Fix abnormal scale up after last cmd finish

When ufshcd_clk_scaling_suspend_work (thread A) running and new command
coming, ufshcd_clk_scaling_start_busy (thread B) may get host_lock after
thread A first time release host_lock. Then thread A second time get
host_lock will set clk_scaling.window_start_t = 0 which scale up clock
abnormal next polling_ms time.  Also inlines another
__ufshcd_suspend_clkscaling calls.

Below is racing step:
1	hba->clk_scaling.suspend_work (Thread A)
	ufshcd_clk_scaling_suspend_work
2		spin_lock_irqsave(hba->host->host_lock, irq_flags);
3		hba->clk_scaling.is_suspended = true;
4		spin_unlock_irqrestore(hba->host->host_lock, irq_flags);
		__ufshcd_suspend_clkscaling
7			spin_lock_irqsave(hba->host->host_lock, flags);
8			hba->clk_scaling.window_start_t = 0;
9			spin_unlock_irqrestore(hba->host->host_lock, flags);

	ufshcd_send_command (Thread B)
		ufshcd_clk_scaling_start_busy
5			spin_lock_irqsave(hba->host->host_lock, flags);
			....
6			spin_unlock_irqrestore(hba->host->host_lock, flags);

Signed-off-by: Peter Wang <peter.wang@mediatek.com>
Link: https://lore.kernel.org/r/20230831130826.5592-3-peter.wang@mediatek.com
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>