s390/sclp: pass timeout as HZ independent value

s390/sclp: pass timeout as HZ independent value

schedule_timeout takes a timeout in jiffies but the code currently is
passing in a constant SDIAS_SLEEP_TICKS, as this is otherwise unused
it is replaced by 500ms as recommended by Michael Holzheu
<holzheu@linux.vnet.ibm.com> and converted with msecs_to_jiffies();
As SDIAS_SLEEP_TICKS was only used in this one location it is dropped.

Patch was compile tested with (s390) defconfig +
CONFIG_MARCH_Z10=y, (implies CONFIG_CRASH_DUMP=y)

Patch is against 4.1-rc5 (localversion-next is -next-20150529)

Link: http://lkml.org/lkml/2015/5/29/235
Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>