PM: subsys_data in struct dev_pm_info need not depend on RM_RUNTIME

The subsys_data field of struct dev_pm_info, introduced by commit
1d2b71f6 (PM / Runtime: Add subsystem
data field to struct dev_pm_info), is going to be used even if
CONFIG_PM_RUNTIME is not set, so move it from under the #ifdef.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>