ACPICA: debugger: add command to dump all fields of particular subtype

In acpiexec, this can be invoked by typing "fields" followed by a
number representing the address space ID of that field.

Signed-off-by: Erik Schmauss <erik.schmauss@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>