PM / Domains: Always enable debugfs support if available

Debugfs support for PM domains is only enabled if both CONFIG_PM_DEBUG
and CONFIG_PM_ADVANCED_DEBUG are enabled. CONFIG_PM_ADVANCED_DEBUG is
described as "extra PM attributes in sysfs for low-level
debugging/testing" which does not seem related.

Given that the debugfs for PM domains only allows users to view the
state of the PM domains, always enable debugfs support for PM domains
if PM domains and debugfs support is enabled.

Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>