ata: ahci_tegra: Read calibration fuse

The original version of the driver did not read the SATA calibration
fuse to remove the dependency to the fuse driver. The fuse driver
is now merged, so add this functionality.

The calibration fuse contains a 2-bit value used to pick a set
of calibration values for the SATA pad.

Signed-off-by: Mikko Perttunen <mperttunen@nvidia.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>