drm/amd/display: Use plane pointer to avoid line breaks

Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Mikita Lipski <Mikita.Lipski@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>