scsi: qedf: remove set but not used variables

Fixes gcc '-Wunused-but-set-variable' warnings:

drivers/scsi/qedf/qedf_els.c: In function 'qedf_process_els_compl':
drivers/scsi/qedf/qedf_els.c:149:20: warning: variable 'sc_cmd' set but not used [-Wunused-but-set-variable]
drivers/scsi/qedf/qedf_els.c:148:28: warning: variable 'task_ctx' set but not used [-Wunused-but-set-variable]
drivers/scsi/qedf/qedf_els.c: In function 'qedf_send_srr':
drivers/scsi/qedf/qedf_els.c:612:6: warning: variable 'sid' set but not used [-Wunused-but-set-variable]

They are never used since introduction.

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Acked-by: Saurav Kashyap <skashyap@marvell.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>