drm/amd/display: fix optimize_bandwidth func pointer for dce80

[Why]
optimize_bandwidth was using dce100_prepare_bandwidth this is incorrect

[How]
change it to dce100_optimize_bandwidth

Signed-off-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Reviewed-by: Charlene Liu <Charlene.Liu@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org