PCI: tegra: Program AFI_CACHE_BAR_{0,1}_{ST,SZ} registers only for Tegra20

Cacheable upstream transactions are supported in Tegra20 and Tegra186
only.

AFI_CACHE_BAR_{0,1}_{ST,SZ} registers are available in Tegra20 to
support cacheable upstream transactions. In Tegra186, AFI_AXCACHE
register is defined instead of AFI_CACHE_BAR_{0,1}_{ST,SZ} to be in line
with its memory subsystem design.

Therefore, program AFI_CACHE_BAR_{0,1}_{ST,SZ} registers only for Tegra20.

Signed-off-by: Manikanta Maddireddy <mmaddireddy@nvidia.com>
[lorenzo.pieralisi@arm.com: updated commit log]
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Thierry Reding <treding@nvidia.com>