Fix the default return value of dm_pool_dec_data_range()

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7LJO8


CVE: NA

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

Commit 26d0b2da ("dm thin metadata: check fail_io before using
data_sm") change the defalut return value of dm_pool_dec_data_range(),
so fix it.

Fixes: 26d0b2da ("dm thin metadata: check fail_io before using data_sm")
Signed-off-by: Li Lingfeng <lilingfeng3@huawei.com>