Functions (disable_all_writeback_pipes_for_stream &
dc_enable_stereo & dc_post_update_surfaces_to_stream)
always return true, there is no need to keep the return value.
This change is to make the code a bit more readable.
Signed-off-by: NBernard Zhao <bernard@vivo.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>