drm/amdgpu: optimize VRAM allocation when using drm buddy

Since the VRAM manager changed from drm mm to drm buddy. It's
not necessary to allocate 2MB aligned VRAM for more than 2MB
unaligned size, and then do trim. This method improves the
allocation efficiency and reduces memory fragmentation.

v2: Correct the remainder operation
Signed-off-by: Shane Xiao <shane.xiao@amd.com>
Reviewed-by: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -453,7 +453,8 @@ static int amdgpu_vram_mgr_new(struct ttm_resource_manager *man,
 		/* Limit maximum size to 2GiB due to SG table limitations */
 		size = min(remaining_size, 2ULL << 30);
 
-		if (size >= (u64)pages_per_block << PAGE_SHIFT)
+		if ((size >= (u64)pages_per_block << PAGE_SHIFT) &&
+				!(size & (((u64)pages_per_block << PAGE_SHIFT) - 1)))
 			min_block_size = (u64)pages_per_block << PAGE_SHIFT;
 
 		cur_size = size;