PCI: iproc: Save host bridge window resource in struct iproc_pcie

The host bridge memory window resource is inserted into the iomem_resource
tree and cannot be deallocated until the host bridge itself is removed.

Previously, the window was on the stack, which meant the iomem_resource
entry pointed into the stack and was corrupted as soon as the probe
function returned, which caused memory corruption and errors like this:

  pcie_iproc_bcma bcma0:8: resource collision: [mem 0x40000000-0x47ffffff] conflicts with PCIe MEM space [mem 0x40000000-0x47ffffff]

Move the memory window resource from the stack into struct iproc_pcie so
its lifetime matches that of the host bridge.

Fixes: c3245a56 ("PCI: iproc: Request host bridge window resources")
Reported-and-tested-by: Rafał Miłecki <zajec5@gmail.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: stable@vger.kernel.org	# v4.8+