drm/amd: Don't try to enable secure display TA multiple times

If the securedisplay TA failed to load the first time, it's unlikely
to work again after a suspend/resume cycle or reset cycle and it appears
to be causing problems in futher attempts.

Fixes: e42dfa66 ("drm/amdgpu: Add secure display TA load for Renoir")
Reported-by: Filip Hejsek <filip.hejsek@gmail.com>
Closes: drm/amd#2633


Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>