eulerfs: remove redundant calculations

uniontech inclusion
category: cleanup
bugzilla: https://gitee.com/openeuler/kernel/issues/I4X47D?from=project-issue
CVE: NA

--------------------------------

The 'left' always is 0.
If it is not 0, it will 'goto out;' from the previous if judgment.
Reviewed-by: NYu Kuai <yukuai3@huawei.com>
Acked-by: NXie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

fs/eulerfs/dax.c

@@ -1172,8 +1172,8 @@ static ssize_t do_mapping_read(struct address_space *mapping,
 			goto out;
 		}
 
-		copied += (nr - left);
-		offset += (nr - left);
+		copied += nr;
+		offset += nr;
 		index += offset >> PAGE_SHIFT;
 		offset &= ~PAGE_MASK;
 	} while (copied < len);