[PATCH] s390: dasd block device driver.

[PATCH] s390: dasd block device driver.

updates for s390 dasd driver

Some problems have been found in the dasd error handling code, they
are fixed by the update to dasd_3990_erp.c.

Dasd is one of only two remaining drivers that use the null
elevator instead of iosched. Appearantly, the null elevator
has some bitrot and can result in random data loss. For now,
we just don't use it.