PCI: tegra: Stop setting pcibios_min_mem

pcibios_min_mem only exists on 32-bit ARM, so using it in pci-tegra.c
prevents the driver from being used on other arches.

In __pci_assign_resource(), we clip the available area based on
PCIBIOS_MIN_MEM.  On 32-bit ARM, this is pcibios_min_mem, with a default
value of 0x01000000.  For Tegra, we discover the space available for PCI
resource allocation from the device tree, and the lowest address that will
ever be available is 0x12000000 (on Tegra124).

The Tegra windows are always higher than the default pcibios_min_mem, so
the __pci_assign_resource() has no effect, so there's no need to adjust
pcibios_min_mem here.

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