drm/amd/display: Fix null-derefs on non-dcn builds

Fixing regression introduced by
'Use real BE and FE index to program regs.'
Signed-off-by: Roman Li <Roman.Li@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -1407,6 +1407,7 @@ static int acquire_first_free_pipe(
 			pipe_ctx->plane_res.xfm = pool->transforms[i];
 			pipe_ctx->plane_res.dpp = pool->dpps[i];
 			pipe_ctx->stream_res.opp = pool->opps[i];
+			if (pool->dpps[i])
 				pipe_ctx->plane_res.mpcc_inst = pool->dpps[i]->inst;
 			pipe_ctx->pipe_idx = i;
 

drivers/gpu/drm/amd/display/dc/dce110/dce110_hw_sequencer.c

@@ -2819,7 +2819,8 @@ static void dce110_apply_ctx_for_surface(
 
 static void dce110_power_down_fe(struct dc *dc, struct pipe_ctx *pipe_ctx)
 {
-	int fe_idx = pipe_ctx->plane_res.mi->inst;
+	int fe_idx = pipe_ctx->plane_res.mi ?
+		pipe_ctx->plane_res.mi->inst : pipe_ctx->pipe_idx;
 
 	/* Do not power down fe when stream is active on dce*/
 	if (dc->current_state->res_ctx.pipe_ctx[fe_idx].stream)