ACPI / scan: Follow priorities of IDs when matching scan handlers

The IDs of ACPI device nodes stored in their pnp.ids member arrays
are sorted by decreasing priority (i.e. the highest-priority ID is
the first entry).  This means that when matching scan handlers to
device nodes, the namespace scanning code should walk the list of
scan handlers for each device node ID instead of walking the list
of device node IDs for each handler (the latter causes the first
handler matching any of the device node IDs to be chosen, although
there may be another handler matching an ID of a higher priority
which should be preferred).  Make the code follow this observation.

This change has been suggested and justified by Toshi Kani.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Toshi Kani <toshi.kani@hp.com>