drm/amd/display: Wrong ifdef guards were used around DML validation

drm/amd/display: Wrong ifdef guards were used around DML validation

[Why]
Wrong guards were causing the debug option not to run.

[How]
Changed the guard to the correct one, matching the rq, ttu, dlg regs struct
members that need to be guarded. Also log a message when validation starts.

Signed-off-by: Jaehyun Chung <jaehyun.chung@amd.com>
Reviewed-by: Alvin Lee <Alvin.Lee2@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>