ACPI / PM: Add functions for manipulating lists of power resources

ACPI device power resources should be reference counted during
device initialization, so that their reference counters are always
up to date.  It is convenient to do that with the help of a function
that will reference count and possibly turn on power resources in
a given list, so introduce that function, acpi_power_on_list().
For symmetry, introduce acpi_power_off_list() for performing the
reverse operation and use the both of them to simplify
acpi_power_transition().

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Len Brown <len.brown@intel.com>