PCI: Preserve resource size during alignment reordering

In d74b9027 ("PCI: Consider additional PF's IOV BAR alignment in sizing
and assigning"), we store additional alignment in realloc_head and take
this into consideration for assignment.

In __assign_resources_sorted(), we changed dev_res->res->start, then used
resource_start() (which depends on res->start), so the recomputed res->end
was completely bogus.  Even if we'd had the correct size, the end would
have been off by one.

Preserve the resource size when we adjust its alignment.

[bhelgaas: changelog]
Fixes: d74b9027 ("PCI: Consider additional PF's IOV BAR alignment in sizing and assigning")
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Wei Yang <weiyang@linux.vnet.ibm.com>
CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>