drm/amd/display: Remove stream_res tg null check in commit planes

[Why]
TG in pipe_ctx stream resource is not null where used in
commit_planes_do_stream_update since it is assigned the
same time the stream is set in pipe_ctx - when the pipe is
acquired. This null check produced a static code analysis
warning and should be removed to avoid similar unnecessary
checks in the future.

[How]
Remove the null check.
Signed-off-by: SivapiriyanKumarasamy <sivapiriyan.kumarasamy@amd.com>
Reviewed-by: Krunoslav Kovac <Krunoslav.Kovac@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/core/dc.c

@@ -1389,7 +1389,6 @@ static void commit_planes_do_stream_update(struct dc *dc,
 					stream_update->adjust->v_total_max);
 
 			if (stream_update->periodic_fn_vsync_delta &&
-					pipe_ctx->stream_res.tg &&
 					pipe_ctx->stream_res.tg->funcs->program_vline_interrupt)
 				pipe_ctx->stream_res.tg->funcs->program_vline_interrupt(
 					pipe_ctx->stream_res.tg, &pipe_ctx->stream->timing,