PCI: tegra: Remove top-level resource from hierarchy

41534e53 ("PCI: tegra: Implement a proper resource hierarchy") did two
things:

  1) It added a top-level resource that encloses all resources declared in
     the DT description, including registers and bridge apertures, and

  2) It requested the bridge apertures, which means the PCI core can track
     the resources used by PCI devices below the bridge.

The latter is necessary, but the former is questionable because there's no
guarantee that the bridge registers and the apertures are contiguous.  In
this example:

  # cat /proc/iomem
  00000000-3fffffff : /pcie-controller@00003000
    00000000-00000fff : /pcie-controller@00003000/pci@1,0
    00003000-000037ff : pads
    00003800-000039ff : afi
    10000000-1fffffff : cs

the resource tree claims that [mem 0x00003a00-0x0fffffff] is consumed by
/pcie-controller@00003000, but it's not mentioned in the DT, and it might
actually be used by other devices.

Remove the top-level resource so we don't claim more than the device
actually consumes.

This reintroduces the problem that we can't match the resources, e.g.,
"pads", "afi", "cs", etc., to the DT device.  I think this should be solved
by having the DT core request all resources of all devices in the DT (it
does not do that today).  If a driver claims the device, it can request the
resources it uses.  For example:

  # cat /proc/iomem
  00000000-00000fff : /pcie-controller@00003000
    00000000-00000fff : /pcie-controller@00003000/pci@1,0
  00003000-000037ff : /pcie-controller@00003000
    00003000-000037ff : pads
  00003800-000039ff : /pcie-controller@00003000
    00003800-000039ff : afi
  10000000-1fffffff : /pcie-controller@00003000
    10000000-1fffffff : cs
  ...

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>