scsi: sg: fix memory leak in sg_build_indirect

hulk inclusion
category: bugfix
bugzilla: 34236
CVE: NA

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Fix a memory leak that occurs when alloc_pages() succeeds several
times before failing. This condition is noticed when rem_sz > 0.

Signed-off-by: Li Bin <huawei.libin@huawei.com>
Reviewed-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>