scsi: mvumi: Fix error return in mvumi_io_attach()

Return PTR_ERR() from the error handling case instead of 0.

Link: https://lore.kernel.org/r/20200910123848.93649-1-jingxiangfeng@huawei.com


Signed-off-by: Jing Xiangfeng <jingxiangfeng@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>