cpuidle: Do not return from cpuidle_play_dead() on callback failures

If the :enter_dead() idle state callback fails for a certain state,
there may be still a shallower state for which it will work.

Because the only caller of cpuidle_play_dead(), native_play_dead(),
falls back to hlt_play_dead() if it returns an error, it should
better try all of the idle states for which :enter_dead() is present
before failing, so change it accordingly.

Also notice that the :enter_dead() state callback is not expected
to return on success (the CPU should be "dead" then), so make
cpuidle_play_dead() ignore its return value.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
Tested-by: Mario Limonciello <mario.limonciello@amd.com> # 6.12-rc7
Reviewed-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
Link: https://patch.msgid.link/3318440.aeNJFYEL58@rjwysocki.net