scsi: qla2xxx: Remove two superfluous if-tests

This patch fixes the following Coverity complaint:

Null-checking sp->u.iocb_cmd.u.ctarg.rsp suggests that it may be null, but
it has already been dereferenced on all paths leading to the check.

See also commit e374f9f5 ("scsi: qla2xxx: Migrate switch registration commands away from mailbox interface") # v4.16.

Cc: Himanshu Madhani <hmadhani@marvell.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Tested-by: Himanshu Madhani <hmadhani@marvell.com>
Reviewed-by: Himanshu Madhani <hmadhani@marvell.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>