PCI: Set under_pref for mem64 resource of pcie device

PCI: Set under_pref for mem64 resource of pcie device

We still get "no compatible bridge window" warning on sparc T5-8
after we add support for 64bit resource parsing for root bus.

 PCI: scan_bus[/pci@300/pci@1/pci@0/pci@6] bus no 8
 PCI: Claiming 0000:00:01.0: Resource 15: 0000800100000000..00008004afffffff [220c]
 PCI: Claiming 0000:01:00.0: Resource 15: 0000800100000000..00008004afffffff [220c]
 PCI: Claiming 0000:02:04.0: Resource 15: 0000800100000000..000080012fffffff [220c]
 PCI: Claiming 0000:03:00.0: Resource 15: 0000800100000000..000080012fffffff [220c]
 PCI: Claiming 0000:04:06.0: Resource 14: 0000800100000000..000080010fffffff [220c]
 PCI: Claiming 0000:05:00.0: Resource 0: 0000800100000000..0000800100001fff [204]
 pci 0000:05:00.0: can't claim BAR 0 [mem 0x800100000000-0x800100001fff]: no compatible bridge window

All the bridges 64-bit resource have pref bit, but the device resource does not
have pref set, then we can not find parent for the device resource,
as we can not put non-pref mem under pref mem.

According to pcie spec errta
https://www.pcisig.com/specifications/pciexpress/base2/PCIe_Base_r2.1_Errata_08Jun10.pdf
page 13, in some case it is ok to mark some as pref.

Only set pref for 64bit mmio when the entire path from the host to the adapter is
over PCI Express.

Fixes: commit d63e2e1f3df9 ("sparc/PCI: Clip bridge windows to fit in upstream windows")
Link: http://lkml.kernel.org/r/CAE9FiQU1gJY1LYrxs+ma5LCTEEe4xmtjRG0aXJ9K_Tsu+m9Wuw@mail.gmail.com
Reported-by: David Ahern <david.ahern@oracle.com>
Tested-by: David Ahern <david.ahern@oracle.com>
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Cc:  <stable@vger.kernel.org> #3.19
(cherry picked from commit ab88cbba3f034f6b2da122280a8000b02fc841dd)