drm/amd/display: Move copy_construct from state_alloc to atomic_check.

Previously atomic_check assumed that dc_state is allocated and filled
in. This is not the case when we hit EDEADLK and have to backup and
retry.

We could change atomic_state_clear but that revealed some other
problems. For now let's create and construct dc_state in atomic_check.

Signed-off-by: Leo (Sunpeng) Li <sunpeng.li@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>