drm/amd/display: Use drm_err() instead of DRM_ERROR in dm_resume()

drm_err() is helpful to show which device had the error. Adjust to
using this instead for error messages.

Reviewed-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Wayne Lin <wayne.lin@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>