regression on suspend/resume for Carrizo

[Tom St Denis]

Hi,

This commit breaks suspend/resume on my Carrizo A12-9800 system.

[root at carrizo linux2]# git bisect bad
7ae4acd21e9e264afb079e23d43bcf2238c7dbea is the first bad commit
commit 7ae4acd21e9e264afb079e23d43bcf2238c7dbea
Author: Leo (Sunpeng) Li <sunpeng.li at amd.com>
Date:   Thu Sep 7 17:05:38 2017 -0400

     drm/amd/display: Match actual state during S3 resume.

     During system suspend, we:

     1. Cache a duplicate of the current DRM atomic state, which calls hooks
        to duplicate our internal states.
     2. Call hooks to disable all functionalities.
     3. System suspended.

     During resume, we attempt to restore the cached state. However, our
     interal states are now stale, since step 1 was done before step 2.
     i.e. our cached state does not reflect the disabled nature of things.

     This change resolves that by destroying all relevant states to reflect
     the actual state during resume.

     Signed-off-by: Leo (Sunpeng) Li <sunpeng.li at amd.com>
     Reviewed-by: Harry Wentland <Harry.Wentland at amd.com>

Tom