drm/amd/display: Initialize psr debug flags to 0

[Why]
Debug flags are not set by default.

[How]
Set debug flags to 0

Signed-off-by: Wyatt Wood <wyatt.wood@amd.com>
Reviewed-by: Anthony Koo <Anthony.Koo@amd.com>
Acked-by: Eryk Brol <eryk.brol@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>