F15tn: Modify devicetree to fix S3 resume

F15tn: Modify devicetree to fix S3 resume

The way that devicetree.cb was configured for the family 15tn boards
was doing... interesting things to the video device initialization.
This was causing S3 resume to fail.

There is a disconnect between how the devicetree should be configured
if there are multiple HT links on the CPU and how it's configured if
there's only one HT link.  These platforms were set up as if they
had multiple HT links, which was causing duplicate instances of
devices in the device list.

The scan for the IO Hub was removed from the northbridge code which
isn't a problem for F15tn devices.

Change-Id: I3556b43027746e36b07de7cb1bece4d1b37a3c34
Signed-off-by: Martin Roth <martin@se-eng.com>
Reviewed-on: http://review.coreboot.org/2160
Tested-by: build bot (Jenkins)
Reviewed-by: Marc Jones <marcj303@gmail.com>