xen/arm: dom0less hwdom construction

xen/arm: dom0less hwdom construction

When creating a hardware domain, have the dom0less code call
construct_hwdom() which is shared with the dom0 code.  The hardware
domain requires building that best matches the dom0 build path.  Re-use
it to keep them in sync.

The device tree node of the dom0less config is now passed into
construct_hwdom().  dom0 uses /chosen for process_shm while a hwdom will
use the value from its dom0less device tree node.

Signed-off-by: Jason Andryuk <jason.andryuk@amd.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>