drm/amd: remove inclusion of non-existing scheduler directory

The scheduler directory was removed via commit 1b1f42d8

 ("drm: move amd_gpu_scheduler into common location")
Remove it from include path.

Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Corentin Labbe <clabbe@baylibre.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>