ovl: update documentation

Two "fixme" items are actually fixed now.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Documentation/filesystems/overlayfs.txt

@@ -194,15 +194,6 @@ If a file with multiple hard links is copied up, then this will
 "break" the link.  Changes will not be propagated to other names
 referring to the same inode.
 
-Symlinks in /proc/PID/ and /proc/PID/fd which point to a non-directory
-object in overlayfs will not contain valid absolute paths, only
-relative paths leading up to the filesystem's root.  This will be
-fixed in the future.
-
-Some operations are not atomic, for example a crash during copy_up or
-rename will leave the filesystem in an inconsistent state.  This will
-be addressed in the future.
-
 Changes to underlying filesystems
 ---------------------------------