drm/amd/display: Always use legacy way of setting cursor on DCE

Some IGT tests fail with the new atomic cursor updates
when running on older DCE-based ASICs. To work around
these issues keep calling the amdgpu_dm_commit_cursors
for each cursor update on DCE, even if those cursor
updates coincide with other plane updates.

Reviewed-by: Agustin Gutierrez <agustin.gutierrez@amd.com>
Reviewed-by: Sun peng Li <sunpeng.li@amd.com>
Acked-by: Wayne Lin <wayne.lin@amd.com>
Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>