s390/dasd: Add missing intensity definition

The definition for the bit that removes the write permission for record
zero when formatting was missing. Add it to complete the list.

Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>
Reviewed-by: Stefan Haberland <sth@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>