PCI: tegra: Remove redundant _data suffix

The struct tegra_pcie_soc_data represents SoC-specific data.  The shorter
name tegra_pcie_soc already describes that accurately enough, so the extra
five characters are redundant.  Also remove the suffix from various
variable names to shorten the code a little.

This also makes this driver more consistent with the naming used in other
drivers that use a similar mechanism to differentiate between various SoC
generations.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>