scsi: ufs-pci: Add LTR support for Intel controllers

Intel host controllers support the setting of latency tolerance.
Accordingly, implement the PM QoS ->set_latency_tolerance() callback. The
raw register values are also exposed via debugfs.

Link: https://lore.kernel.org/r/20200827072030.24655-1-adrian.hunter@intel.com


Fixes: 8c09d752 ("scsi: ufshdc-pci: Add Intel PCI IDs for EHL")
Fixes: 1ab27c9c ("ufs: Add support for clock gating")
Reviewed-by: Avri Altman <avri.altman@wdc.com>
Acked-by: Stanley Chu <stanley.chu@mediatek.com>
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>