PCI: Clear IORESOURCE_UNSET when reverting to firmware-assigned address

PCI: Clear IORESOURCE_UNSET when reverting to firmware-assigned address

If pci_assign_resource() fails to assign space for a BAR, we may restore
the BAR to whatever firmware left there at boot-time (this depends on
whether the arch implements pcibios_retrieve_fw_addr()).  The messages we
print are not as useful as they could be:

  pci 0000:00:01.0: BAR 15: assigned [mem 0xc0000000-0xc01fffff 64bit pref]
  pci 0000:01:00.0: BAR 0: no space for [mem size 0x10000000 pref]
  pci 0000:01:00.0: BAR 0: trying firmware assignment [mem size 0x10000000 pref]
  pci 0000:01:00.0: BAR 0: [mem size 0x10000000 pref] conflicts with PCI Bus 0000:00 [mem 0xc0000000-0xffffffff window]

The last two lines should contain the actual BAR address, not the size.
Clear IORESOURCE_UNSET so we print the address.  If requesting the
firmware-assigned resource fails, mark it IORESOURCE_UNSET again.

This is a cosmetic change to clarify the message: previously, if
pci_revert_fw_address() succeeded, pci_assign_resource() cleared
IORESOURCE_UNSET anyway, so this isn't really a functional change.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=85491#c50
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>