PM / Domains: Fix default system suspend/resume operations

Commit d23b9b00cdde5c93b914a172cecd57d5625fcd04 (PM / Domains: Rework
system suspend callback routines (v2)) broke the system suspend and
resume handling by devices belonging to generic PM domains, because
it used freeze/thaw callbacks instead of suspend/resume ones and
didn't initialize device callbacks for system suspend/resume
properly at all.  Fix those problems.

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