drm/amd/display: Fix Makefile copyright notices

Leftover copy pasta from original code.
Reviewed-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: Harry.Wentland@amd.com

drivers/gpu/drm/amd/display/dc/dcn301/Makefile

-#
-# (c) Copyright 2020 Advanced Micro Devices, Inc. All the rights reserved
-#
-#  All rights reserved.  This notice is intended as a precaution against
-#  inadvertent publication and does not imply publication or any waiver
-#  of confidentiality.  The year included in the foregoing notice is the
-#  year of creation of the work.
-#
-#  Authors: AMD
+# SPDX-License-Identifier: MIT
+# Copyright © 2024 Advanced Micro Devices, Inc. All rights reserved.
 #
 # Makefile for dcn30.
 

drivers/gpu/drm/amd/display/dc/dcn31/Makefile

+# SPDX-License-Identifier: MIT
+# Copyright © 2024 Advanced Micro Devices, Inc. All rights reserved.
 #
-# Copyright 2020 Advanced Micro Devices, Inc. All the rights reserved
-#
-#  All rights reserved.  This notice is intended as a precaution against
-#  inadvertent publication and does not imply publication or any waiver
-#  of confidentiality.  The year included in the foregoing notice is the
-#  year of creation of the work.
-#
-#  Authors: AMD
 #
 # Makefile for dcn31.
 

drivers/gpu/drm/amd/display/dc/dcn314/Makefile

-#
-# (c) Copyright 2022 Advanced Micro Devices, Inc. All the rights reserved
-#
-#  All rights reserved.  This notice is intended as a precaution against
-#  inadvertent publication and does not imply publication or any waiver
-#  of confidentiality.  The year included in the foregoing notice is the
-#  year of creation of the work.
-#
-#  Authors: AMD
+# SPDX-License-Identifier: MIT
+# Copyright © 2024 Advanced Micro Devices, Inc. All rights reserved.
 #
 # Makefile for dcn314.
 

drivers/gpu/drm/amd/display/dc/dcn401/Makefile

-#
-# Copyright © 2023 Advanced Micro Devices, Inc. All rights reserved.
-#
+# SPDX-License-Identifier: MIT
+# Copyright © 2024 Advanced Micro Devices, Inc. All rights reserved.
 
 DCN401 += dcn401_dio_link_encoder.o
 DCN401 += dcn401_dio_stream_encoder.o