Add crc7 and crc64 to HOWTO

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/HOWTO b/HOWTO
index e693d7a..b862d74 100644
--- a/HOWTO
+++ b/HOWTO
@@ -574,12 +574,19 @@
 			md5	Use an md5 sum of the data area and store
 				it in the header of each block.
 
+			crc64	Use an experimental crc64 sum of the data
+				area and store it in the header of each
+				block.
+
 			crc32	Use a crc32 sum of the data area and store
 				it in the header of each block.
 
 			crc16	Use a crc16 sum of the data area and store
 				it in the header of each block.
 
+			crc7	Use a crc7 sum of the data area and store
+				it in the header of each block.
+
 			null	Only pretend to verify. Useful for testing
 				internals with ioengine=null, not for much
 				else.