Documentation: update cgroupfs mount point

According to commit 676db4af04 ("cgroupfs: create /sys/fs/cgroup to
mount cgroupfs on") the canonical mountpoint for the cgroup filesystem
is /sys/fs/cgroup.  Hence, this should be used in the documentation.

Signed-off-by: Jörg Sommer <joerg@alea.gnuu.de>
Acked-by: Paul Menage <menage@google.com>
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Documentation/accounting/cgroupstats.txt

@@ -21,7 +21,7 @@ information will not be available.
 To extract cgroup statistics a utility very similar to getdelays.c
 has been developed, the sample output of the utility is shown below
 
-~/balbir/cgroupstats # ./getdelays  -C "/cgroup/a"
+~/balbir/cgroupstats # ./getdelays  -C "/sys/fs/cgroup/a"
 sleeping 1, blocked 0, running 1, stopped 0, uninterruptible 0
-~/balbir/cgroupstats # ./getdelays  -C "/cgroup"
+~/balbir/cgroupstats # ./getdelays  -C "/sys/fs/cgroup"
 sleeping 155, blocked 0, running 1, stopped 0, uninterruptible 2