scsi: ufshcd: Update the set frequency to devfreq

scsi: ufshcd: Update the set frequency to devfreq

Currently, the frequency that devfreq provides the driver always leads the
clocks to be scaled up.  Hence, round the clock-rate to the nearest
frequency before deciding to scale.

Also update the devfreq statistics of current frequency.

Link: https://lore.kernel.org/r/d0c6c22455811e9f0eda01f9bc70d1398b51b2bd.1585160616.git.asutoshd@codeaurora.org
Acked-by: Avri Altman <Avri.Altman@wdc.com>
Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>