udf: Update mount option documentation

Update documentation of uid and gid mount options.
Reviewed-by: Pali Rohár <pali.rohar@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>

Documentation/filesystems/udf.txt

@@ -36,18 +36,14 @@ The following mount options are supported:
 	iocharset=	Set the NLS character set
 
 The uid= and gid= options need a bit more explaining.  They will accept a
-decimal numeric value which will be used as the default ID for that mount.
-They will also accept the string "ignore" and "forget".  For files on the disk
-that are owned by nobody ( -1 ), they will instead look as if they are owned
-by the default ID.  The ignore option causes the default ID to override all
-IDs on the disk, not just -1.  The forget option causes all IDs to be written
-to disk as -1, so when the media is later remounted, they will appear to be
-owned by whatever default ID it is mounted with at that time.
+decimal numeric value and all inodes on that mount will then appear as
+belonging to that uid and gid.  Mount options also accept the string "forget".
+The forget option causes all IDs to be written to disk as -1 which is a way
+of UDF standard to indicate that IDs are not supported for these files .
 
-For typical desktop use of removable media, you should set the ID to that
-of the interactively logged on user, and also specify both the forget and
-ignore options.  This way the interactive user will always see the files
-on the disk as belonging to him.
+For typical desktop use of removable media, you should set the ID to that of
+the interactively logged on user, and also specify the forget option.  This way
+the interactive user will always see the files on the disk as belonging to him.
 
 The remaining are for debugging and disaster recovery: