drm/amd/display: fix HDCP reset sequence on reinitialize

[why]
When setup is called after hdcp has already setup,
it would cause to disable HDCP flow won’t execute.

[how]
Don't clean up hdcp content to be 0.

Signed-off-by: Brandon Syu <Brandon.Syu@amd.com>
Reviewed-by: Wenjing Liu <Wenjing.Liu@amd.com>
Acked-by: Wayne Lin <waynelin@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>