PCI: iova RB tree setup tweak

The following patch merges two functions into one allowing for a 3%
reduction in overhead in locating, allocating and inserting pages for
use in IOMMU operations.

Its a bit of a eye-crosser so I welcome any RB-tree / MM experts to take
a look.  It works by re-using some of the information gathered in the
search for the pages to use in setting up the IOTLB's in the insertion
of the iova structure into the RB tree.

Signed-off-by:  <mgross@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>