drm/amdgpu: Remove trailing space

Clean up trailing space in file sienna_cichlid_ppt.c.
Signed-off-by: Elena Sakhnovitch <elena.sakhnovitch@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>