drm/amd/display: Destroy cached state in complete() callback

[Why]
When the suspend sequence has been aborted after prepare() but
before suspend() the resume() callback never gets called. The PM core
will call complete() when this happens. As the state has been cached
in prepare() it needs to be destroyed in complete() if it's still around.

[How]
Create a helper for destroying cached state and call it both in resume()
and complete() callbacks. If resume has been called the state will be
destroyed and it's a no-op for complete().  If resume hasn't been called
(such as an aborted suspend) then destroy the state in complete().

Fixes: 50e0bae3 ("drm/amd/display: Add and use new dm_prepare_suspend() callback")
Reviewed-by: Alex Hung <alex.hung@amd.com>
Link: https://lore.kernel.org/r/20250602014432.3538345-4-superm1@kernel.org


Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>