s390/dcssblk: correct out of bounds array indexes
s390/dcssblk: correct out of bounds array indexes

Fix a couple of warnings like this:

[linux-4.2-rc7/drivers/s390/block/dcssblk.c:553]:
   (style) Array index 'j' is used before limits check.

Reported-by: David Binderman <b6d239d25020cc5e235b79047ed71f02d7363ad6@hotmail.com>
Signed-off-by: Martin Schwidefsky <52616596d8f5df0d597e85ab515377f92f939c68@de.ibm.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs