Revert "drm/amd/display: cache trace buffer size"

Revert commit 257e9891 ("drm/amd/display: cache trace buffer size")
to fix regression found in tests.

Acked-by: Stylon Wang <stylon.wang@amd.com>
Signed-off-by: Leo Ma <hanghong.ma@amd.com>
Reviewed-by: Josip Pavic <Josip.Pavic@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>