Documentation: cgroups: just fix a few typos

Just fix some typos in blkio-controller.txt, freezer-subsystem.txt,
unified-hierarchy.txt.

Signed-off-by: Yuan Sun <[e-mail]>
Signed-off-by: Jonathan Corbet <[e-mail]>

Documentation/cgroups/blkio-controller.txt

···
 - At macro level, first dd should finish first. To get more precise data, keep
   on looking at (with the help of script), at blkio.disk_time and
   blkio.disk_sectors files of both test1 and test2 groups. This will tell how
-  much disk time (in milli seconds), each group got and how many secotors each
+  much disk time (in milliseconds), each group got and how many sectors each
   group dispatched to the disk. We provide fairness in terms of disk time, so
   ideally io.disk_time of cgroups should be in proportion to the weight.
 

Documentation/cgroups/freezer-subsystem.txt

···
 expected.
 
 The cgroup freezer is hierarchical. Freezing a cgroup freezes all
-tasks beloning to the cgroup and all its descendant cgroups. Each
+tasks belonging to the cgroup and all its descendant cgroups. Each
 cgroup has its own state (self-state) and the state inherited from the
 parent (parent-state). Iff both states are THAWED, the cgroup is
 THAWED.

Documentation/cgroups/unified-hierarchy.txt

···
 	${R|W}BPS are read/write bytes per second and ${R|W}IOPS are
 	read/write IOs per second.  "max" indicates no limit.  Writing
 	to the file follows the same format but the individual
-	settings may be ommitted or specified in any order.
+	settings may be omitted or specified in any order.
 
 	This file is available only on non-root cgroups.