scsi: be2iscsi: Fix use-after-free during IP updates

This fixes a bug found by Lv Yunlong where, because beiscsi_exec_nemb_cmd()
frees memory for the be_dma_mem cmd(), we can access freed memory when
beiscsi_if_clr_ip()/beiscsi_if_set_ip()'s call to beiscsi_exec_nemb_cmd()
fails and we access the freed req. This fixes the issue by having the
caller free the cmd's memory.

Link: https://lore.kernel.org/r/20210701190840.175120-1-michael.christie@oracle.com


Reported-by: Lv Yunlong <lyl2019@mail.ustc.edu.cn>
Signed-off-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>