c770cb4c ("PCI: Mark invalid BARs as unassigned") sets IORESOURCE_UNSET
if we fail to claim a resource.  If we tried to claim a bridge window,
failed, clipped the window, and tried to claim the clipped window, we
failed again because of IORESOURCE_UNSET:

  pci_bus 0000:00: root bus resource [mem 0xc0000000-0xffffffff window]
  pci 0000:00:01.0: can't claim BAR 15 [mem 0xbdf00000-0xddefffff 64bit pref]: no compatible bridge window
  pci 0000:00:01.0: [mem size 0x20000000 64bit pref] clipped to [mem size 0x1df00000 64bit pref]
  pci 0000:00:01.0:   bridge window [mem size 0x1df00000 64bit pref]
  pci 0000:00:01.0: can't claim BAR 15 [mem size 0x1df00000 64bit pref]: no address assigned

The 00:01.0 window started as [mem 0xbdf00000-0xddefffff 64bit pref].  That
starts before the host bridge window [mem 0xc0000000-0xffffffff window], so
we clipped the 00:01.0 window to [mem 0xc0000000-0xddefffff 64bit pref].
But we left it marked IORESOURCE_UNSET, so the second claim failed when it
should have succeeded.

This means downstream devices will also fail for lack of resources, e.g.,
in the bugzilla below,

  radeon 0000:01:00.0: Fatal error during GPU init

Clear IORESOURCE_UNSET when we clip a bridge window.  Also clear
IORESOURCE_UNSET in our copy of the unclipped window so we can see exactly
what the original window was and how it now fits inside the upstream
window.

Fixes: c770cb4c ("PCI: Mark invalid BARs as unassigned")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=85491#c47Based-on-patch-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Based-on-patch-by: Yinghai Lu <yinghai@kernel.org>
Tested-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Yinghai Lu <yinghai@kernel.org>
CC: stable@vger.kernel.org	# v4.1+