drm/amd/display: Replace for loop w/ function call

[WHY]
A function to adjust DPP clocks with DTO already exists; function code
is identical to the code replaced here

Signed-off-by: Wesley Chalmers <Wesley.Chalmers@amd.com>
Reviewed-by: Charlene Liu <Charlene.Liu@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>