[Why]

When entering S3, amdgpu first calls DRM to cache the current atomic
state, then commit the 'all-disabled' state. This sets dc->current_state
to point at the private atomic object's dm_atomic_state->context, as
any regular atomic commit would.

Afterwards, amdgpu_dm calls dc_set_power_state() with S3 power state.
This invalidates dc->current_state by wiping it to 0, consequently
wiping dm_atomic_state->context.

During resume, the cached atomic state is restored. When getting the
private object however, the dm_atomic_state - containing the wiped
context - is duplicated into the atomic state. This causes DC validation
to fail during atomic check, as necessary function pointers in dc_state
are now NULL.

[How]

Recreate the private object's dm_atomic_state->context during resume,
restoring any static values such as function pointers.

A TODO item is added to move static read-only values out of dc_state -
they shouldn't be there anyways.
Signed-off-by: Leo Li <sunpeng.li@amd.com>
Reviewed-by: Nicholas Kazlauskas <Nicholas.Kazlauskas@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>