scsi: ufs: Clean up ufshcd_scale_clks() and clock scaling error out path

scsi: ufs: Clean up ufshcd_scale_clks() and clock scaling error out path

This change introduces a func ufshcd_set_clk_freq() to explicitly set clock
frequency so that it can be used in reset_and_restore path and in
ufshcd_scale_clks(). This change also cleans up the clock scaling error out
path.

[mkp: commit desc]

Link: https://lore.kernel.org/r/1585214742-5466-2-git-send-email-cang@codeaurora.org
Fixes: a3cd5ec55f6c ("scsi: ufs: add load based scaling of UFS gear")
Reviewed-by: Bean Huo <beanhuo@micron.com>
Acked-by: Avri Altman <Avri.Altman@wdc.com>
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>
Signed-off-by: Can Guo <cang@codeaurora.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>