PCI: make re-allocation try harder by reassigning ranges higher in the heirarchy

PCI: make re-allocation try harder by reassigning ranges higher in the heirarchy

On a system with devices that support SRIOV connected to a pcie switch
to pcie root port:

 +-[0000:80]-+-00.0-[81-8f]--
 |           +-01.0-[90-9f]--
 |           +-02.0-[a0-af]----00.0-[a1-a3]--+-02.0-[a2]--+-00.0 Oracle Corporation Device 207a
 |           |                               \-03.0-[a3]--+-00.0 Oracle Corporation Device 207a
 |           +-02.2-[b0-bf]----00.0-[b1-b3]--+-02.0-[b2]--+-00.0 Oracle Corporation Device 207a
 |           |                               \-03.0-[b3]--+-00.0 Oracle Corporation Device 207a

When the BIOS does not assign resources for SRIOV BARs, kernel pci
reallocation only goes up one bridge and then gives up, failing to to
get resources for all sSRIOV BARs, even though the range is large enough
in the peer root bus.

Specifically, only the bridge at the a1:02.0 level has its resources
cleared and reallocated.  The kernel does not go up to clear the bridge
at the 80:02.0 level.

To make it go to upper levels, during retry, we need to treat "good to have"
resources as "must have".

Only on the last try will we treat good to have resources as optional.
At that time, parent bridge resources will already have been released so
we'll have a chance to get everything assigned with must_have plus
good_to_have for all child devices.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>