drm/amd/display: add default clocks if not able to fetch them

dm_pp_get_clock_levels_by_type needs to add the default clocks
to the powerplay case as well.  This was accidently dropped.

Fixes: b3ea88fe ("drm/amd/powerplay: add get_clock_by_type interface for display")
Bug: https://gitlab.freedesktop.org/drm/amd/issues/906


Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org