Revert "drm/amdgpu: fix start calculation in amdgpu_vram_mgr_new"

This reverts commit 5e3f1e77.

This is part of a revert of the following commits:
commit 708d19d9 ("drm/amdgpu: move internal vram_mgr function into the C file")
commit 5e3f1e77 ("drm/amdgpu: fix start calculation in amdgpu_vram_mgr_new")
commit c9cad937 ("drm/amdgpu: add drm buddy support to amdgpu")

[WHY]
Few users reported garbaged graphics as soon as x starts,
reverting until this can be resolved.
Signed-off-by: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220708093047.492662-2-Arunpravin.PaneerSelvam@amd.com

drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c

@@ -496,23 +496,17 @@ static int amdgpu_vram_mgr_new(struct ttm_resource_manager *man,
 			list_splice_tail(trim_list, &vres->blocks);
 	}
 
-	vres->base.start = 0;
-	list_for_each_entry(block, &vres->blocks, link) {
-		unsigned long start;
-
-		start = amdgpu_vram_mgr_block_start(block) +
-			amdgpu_vram_mgr_block_size(block);
-		start >>= PAGE_SHIFT;
-
-		if (start > vres->base.num_pages)
-			start -= vres->base.num_pages;
-		else
-			start = 0;
-		vres->base.start = max(vres->base.start, start);
-
+	list_for_each_entry(block, &vres->blocks, link)
 		vis_usage += amdgpu_vram_mgr_vis_size(adev, block);
+
+	block = amdgpu_vram_mgr_first_block(&vres->blocks);
+	if (!block) {
+		r = -EINVAL;
+		goto error_fini;
 	}
 
+	vres->base.start = amdgpu_vram_mgr_block_start(block) >> PAGE_SHIFT;
+
 	if (amdgpu_is_vram_mgr_blocks_contiguous(&vres->blocks))
 		vres->base.placement |= TTM_PL_FLAG_CONTIGUOUS;