scsi: ufs: disable clock scaling

Disable clock scaling to avoid costly workqueue overheads.

Power test results on Blueline:
[without this change]
  Suspend: 9.75mA
  Idle: 238.26mA
  Camera Preview: 1309.99mA
  Partial Wake Lock: 13.67mA
[with this change - disable clock scaling]
  Suspend: 9.73mA (-0.21%)
  Idle: 215.87mA (-9.4%)
  Camera Preview: 1181.71mA (-9.79%)
  Partial Wake Lock: 13.85mA (+1.32%)

Bug: 78601190
Signed-off-by: Mimi Wu <mimiwu@google.com>
Change-Id: I09f07619ab3e11b05149358c1d06b0d1039decf3