drm/amd/display: Revert update clk_mgr for vg

This reverts commit 2208f39c.
It caused a regression in internal FPGA tests.

Signed-off-by: Eric Bernstein <Eric.Bernstein@amd.com>
Reviewed-by: Eric Yang <eric.yang2@amd.com>
Acked-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>