drm/amd/display: add dummy functions to smu for Renoir Silicon Diags

[Why]
Previously only dummy functions were added in Diags for FPGA.
On silicon, this would lead to a segmentation fault on silicon diags.

[How]
Check if diags silicon and if so, add dummy functions.

Signed-off-by: Sung Lee <sung.lee@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Reviewed-by: Roman Li <Roman.Li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>