drm/amd/display: Don't treat missing command table as failure

[Why]
With the fallback case in place for command table offloading via DMCUB
it's no longer an error for the command table to be missing specific
entries.

[How]
Drop the BREAK_TO_DEBUGGER();

Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Reviewed-by: Chris Park <Chris.Park@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>