PCI: tegra: Use bus->sysdata to store and get host private data

Tegra host driver is using pci_find_host_bridge() to get private data;
this can be easily avoided by using bus->sysdata to store and get private
data removing the pci_find_host_bridge() dependency.

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