drm/amd/display: clean up some inconsistent indenting

Eliminate the follow smatch warning:
drivers/gpu/drm/amd/amdgpu/../display/dc/core/dc.c:3151 commit_planes_for_stream() warn: inconsistent indenting

Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>