inotify: update documentation to reflect code changes

The inotify interface has changed a lot.  The user interface was too
old, and the kernel interface was removed by Eric Paris in commit:
2dfc1cae inotify: remove inotify in kernel interface.

Signed-off-by: Zhang Zhen <zhenzhang.zhang@huawei.com>
Cc: Wang Kai <morgan.wang@huawei.com>
Cc: Eric Paris <eparis@parisplace.org>
Cc: Robert Love <robert.w.love@intel.com>
Cc: John McCutchan <john@johnmccutchan.com>
Cc: Heinrich Schuchardt <xypron.glpk@gmx.de>
Acked-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>