udf: Update Kconfig description

Update description of UDF in Kconfig to mention that UDF is also
suitable for removable USB disks.
Signed-off-by: Jan Kara <jack@suse.cz>

fs/udf/Kconfig

@@ -2,10 +2,12 @@ config UDF_FS
 	tristate "UDF file system support"
 	select CRC_ITU_T
 	help
-	  This is the new file system used on some CD-ROMs and DVDs. Say Y if
-	  you intend to mount DVD discs or CDRW's written in packet mode, or
-	  if written to by other UDF utilities, such as DirectCD.
-	  Please read <file:Documentation/filesystems/udf.txt>.
+	  This is a file system used on some CD-ROMs and DVDs. Since the
+	  file system is supported by multiple operating systems and is more
+	  compatible with standard unix file systems, it is also suitable for
+	  removable USB disks. Say Y if you intend to mount DVD discs or CDRW's
+	  written in packet mode, or if you want to use UDF for removable USB
+	  disks. Please read <file:Documentation/filesystems/udf.txt>.
 
 	  To compile this file system support as a module, choose M here: the
 	  module will be called udf.