with xlv2 format we never had to fill in checksumInfo() (#17963)

- this PR avoids sending a large ChecksumInfo slice
  when its not needed

- also for a file with XLV2 format there is no reason
  to allocate Checksum slice while reading

cmd/erasure-object.go

@@ -960,11 +960,6 @@ func (er erasureObjects) putMetacacheObject(ctx context.Context, key string, r *
 		}
 		partsMetadata[i].Data = inlineBuffers[i].Bytes()
 		partsMetadata[i].AddObjectPart(1, "", n, data.ActualSize(), modTime, index, nil)
-		partsMetadata[i].Erasure.AddChecksumInfo(ChecksumInfo{
-			PartNumber: 1,
-			Algorithm:  DefaultBitrotAlgorithm,
-			Hash:       bitrotWriterSum(w),
-		})
 	}
 
 	// Fill all the necessary metadata.
@@ -1296,11 +1291,6 @@ func (er erasureObjects) putObject(ctx context.Context, bucket string, object st
 		}
 		// No need to add checksum to part. We already have it on the object.
 		partsMetadata[i].AddObjectPart(1, "", n, data.ActualSize(), modTime, compIndex, nil)
-		partsMetadata[i].Erasure.AddChecksumInfo(ChecksumInfo{
-			PartNumber: 1,
-			Algorithm:  DefaultBitrotAlgorithm,
-			Hash:       bitrotWriterSum(w),
-		})
 		partsMetadata[i].Versioned = opts.Versioned || opts.VersionSuspended
 	}