IB/iser: Remove unnecessary local variable

The 'error' variable is no longer needed,as iscsi_iser_mtask_xmit can
return the result of iser_send_control(conn,task) directly.

Signed-off-by: Li Jun <lijun01@kylinos.cn>
Link: https://patch.msgid.link/20250604102049.130039-1-lijun01@kylinos.cn


Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Acked-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>