drm/amd/display: Move DPM clk read to clk_mgr_construct in DCN42

drm/amd/display: Move DPM clk read to clk_mgr_construct in DCN42

[Why&How]
The DPM clocks on DCN42 are currently read on every dm_resume, which can
cause in gpu memory freeing while the device is still in suspend.

Move the DPM clock read functionality to clk_mgr_construct() so it
completes once on driver enablement.

Reviewed-by: Charlene Liu <charlene.liu@amd.com>
Signed-off-by: Ivan Lipski <ivan.lipski@amd.com>
Signed-off-by: Dmytro Laktyushkin <dmytro.laktyushkin@amd.com>
Signed-off-by: Chuanyu Tseng <chuanyu.tseng@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>