cgroup: remove "no" prefixed mount options

30312730 ("cgroup: Add "no" prefixed mount options") added "no" prefixed
mount options to allow turning them off and 6a010a49 ("cgroup: Make
!percpu threadgroup_rwsem operations optional") added one more "no" prefixed
mount option. However, Michal pointed out that the "no" prefixed options
aren't necessary in allowing mount options to be turned off:

  # grep group /proc/mounts
  cgroup2 /sys/fs/cgroup cgroup2 rw,nosuid,nodev,relatime,nsdelegate,memory_recursiveprot 0 0
  # mount -o remount,nsdelegate,memory_recursiveprot none /sys/fs/cgroup
  # grep cgroup /proc/mounts
  cgroup2 /sys/fs/cgroup cgroup2 rw,relatime,nsdelegate,memory_recursiveprot 0 0

Note that this is different from the remount behavior when the mount(1) is
invoked without the device argument - "none":

 # grep cgroup /proc/mounts
 cgroup2 /sys/fs/cgroup cgroup2 rw,nosuid,nodev,noexec,relatime,nsdelegate,memory_recursiveprot 0 0
 # mount -o remount,nsdelegate,memory_recursiveprot /sys/fs/cgroup
 # grep cgroup /proc/mounts
 cgroup2 /sys/fs/cgroup cgroup2 rw,nosuid,nodev,noexec,relatime,nsdelegate,memory_recursiveprot 0 0

While a bit confusing, given that there is a way to turn off the options,
there's no reason to have the explicit "no" prefixed options. Let's remove
them.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>