mount: add note about another flags for "remount,bind"

mount: add note about another flags for "remount,bind"

The man page is talking about read-only bind mounts (-o
remount,bind,ro), but this feature also works for another VFS flags
like nodev, suid, etc. For example:

 mount -o remount,bind,noatime /mountpoint

is a valid command.

Addresses: https://github.com/karelzak/util-linux/issues/342
Signed-off-by: Karel Zak <kzak@redhat.com>