amd/display: downgrade validation failure log level

In amdgpu_dm_atomic_check, dc_validate_global_state is called. On
failure this logs a warning to the kernel journal. However warnings
shouldn't be used for atomic test-only commit failures: user-space
might be perfoming a lot of atomic test-only commits to find the
best hardware configuration.

Downgrade the log to a regular DRM atomic message. While at it, use
the new device-aware logging infrastructure.

This fixes error messages in the kernel when running gamescope [1].

[1]: https://github.com/Plagman/gamescope/issues/245



Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Simon Ser <contact@emersion.fr>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Harry Wentland <hwentlan@amd.com>
Cc: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>