This is the closest way to disabling it without using the "libata.force=noncq" kernel boot option is to set the queue to a depth of 1 which doesn't actually disable it.
Change the sdc below to match the device you want to disable NCQ for.
[root@officebox ~]# echo "1" > /sys/block/sdc/device/queue_depth
Errors that indicate you are having a performance issue are these in messages or dmesg relating to N........
[ 12.460014] ata1: SRST failed (errno=-16)
[ 17.626677] ata1: link is slow to respond, please be patient (ready=0)
[ 22.480011] ata1: SRST failed (errno=-16)
[ 27.646681] ata1: link is slow to respond, please be patient (ready=0)
[ 38.106817] ata1.01: failed to IDENTIFY (INIT_DEV_PARAMS failed, err_mask=0x80)
[ 48.266676] ata1: link is slow to respond, please be patient (ready=0)........