block/switching-sched.txt: Update to blk-mq schedulers

Remove references to CFQ and legacy block layer which are gone.
Update example with what's available under blk-mq.
Signed-off-by: Andreas Herrmann <aherrmann@suse.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Documentation/block/switching-sched.txt

@@ -13,11 +13,9 @@ you can do so by typing:
 
 # mount none /sys -t sysfs
 
-As of the Linux 2.6.10 kernel, it is now possible to change the
-IO scheduler for a given block device on the fly (thus making it possible,
-for instance, to set the CFQ scheduler for the system default, but
-set a specific device to use the deadline or noop schedulers - which
-can improve that device's throughput).
+It is possible to change the IO scheduler for a given block device on
+the fly to select one of mq-deadline, none, bfq, or kyber schedulers -
+which can improve that device's throughput.
 
 To set a specific scheduler, simply do this:
 
@@ -30,8 +28,8 @@ The list of defined schedulers can be found by simply doing
 a "cat /sys/block/DEV/queue/scheduler" - the list of valid names
 will be displayed, with the currently selected scheduler in brackets:
 
-# cat /sys/block/hda/queue/scheduler
-noop deadline [cfq]
-# echo deadline > /sys/block/hda/queue/scheduler
-# cat /sys/block/hda/queue/scheduler
-noop [deadline] cfq
+# cat /sys/block/sda/queue/scheduler
+[mq-deadline] kyber bfq none
+# echo none >/sys/block/sda/queue/scheduler
+# cat /sys/block/sda/queue/scheduler
+[none] mq-deadline kyber bfq