drm/amd/display: Update hubbub description comment

Description for DCHUBBUB_TEST_DEBUG_DATA is changed to avoid any future confusions.

Signed-off-by: Peikang Zhang <peikang.zhang@amd.com>
Reviewed-by: Aric Cyr <Aric.Cyr@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>