xl: Fix typo in PutObjectPart when part size is 10Mb (#6574)

PutObjectPart forgot to allocate buffer memory when the size
of the uploaded part is exactly equal to blockSizeV1 = 10 Mb.

cmd/xl-v1-multipart.go

@@ -359,7 +359,7 @@ func (xl xlObjects) PutObjectPart(ctx context.Context, bucket, object, uploadID
 	switch size := data.Size(); {
 	case size == 0:
 		buffer = make([]byte, 1) // Allocate atleast a byte to reach EOF
-	case size == -1 || size > blockSizeV1:
+	case size == -1 || size >= blockSizeV1:
 		buffer = xl.bp.Get()
 		defer xl.bp.Put(buffer)
 	case size < blockSizeV1: