Make pci_claim_resource() use request_resource() rather than insert_resource()

This function has traditionally used "insert_resource()", because before
commit cebd78a8 ("Fix pci_claim_resource") it used to just insert the
resource into whatever root resource tree that was indicated by
"pcibios_select_root()".

So there Matthew fixed it to actually look up the proper parent
resource, which means that now it's actively wrong to then traverse the
resource tree any more: we already know exactly where the new resource
should go.

And when we then did commit a76117df

 ("x86: Use pci_claim_resource"),
which changed the x86 PCI code from the open-coded

	pr = pci_find_parent_resource(dev, r);
	if (!pr || request_resource(pr, r) < 0) {

to using

	if (pci_claim_resource(dev, idx) < 0) {

that "insert_resource()" now suddenly became a problem, and causes a
regression covered by

	http://bugzilla.kernel.org/show_bug.cgi?id=13891

which this fixes.

Reported-and-tested-by: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Matthew Wilcox <willy@linux.intel.com>
Cc: Andrew Patterson <andrew.patterson@hp.com>
Cc: Linux PCI <linux-pci@vger.kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>