drm/amd/display: Don't overwrite dce60_clk_mgr

dc_clk_mgr_create accidentally overwrites the dce60_clk_mgr
with the dce_clk_mgr, causing incorrect behaviour on DCE6.
Fix it by removing the extra dce_clk_mgr_construct.

Fixes: 62eab49f ("drm/amd/display: hide VGH asic specific structs")
Reviewed-by: Rodrigo Siqueira <siqueira@igalia.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit bbddcbe3)
Cc: stable@vger.kernel.org