drm/amd/display: Don't print errors for nonexistent connectors

When getting the number of connectors, the VBIOS reports
the number of valid indices, but it doesn't say which indices
are valid, and not every valid index has an actual connector.
If we don't find a connector on an index, that is not an error.

Considering these are not actual errors, don't litter the logs.

Fixes: 60df5628 ("drm/amd/display: handle invalid connector indices")
Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Rodrigo Siqueira <siqueira@igalia.com>
Reviewed-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 249d4bc5)