scsi: ufs: modify devfreq profile to support multiple UFS hosts

This change makes UFS devfreq profile a private member of clk_scaling so
that each UFS hba device can have its own devfreq profile data.

Change-Id: I653ff4b649c5431ade28683c219709f8767af002
Signed-off-by: Can Guo <cang@codeaurora.org>