s390x: Drop useless casts

s390x: Drop useless casts

An upcoming Coccinelle cleanup script wanted to reformat the casts
present in this file - but on closer look, we don't need the casts
at all because C automatically converts void* to any other pointer.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20170405194741.18956-4-eblake@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
(cherry picked from commit cb55c19a26d6928b445f1bd9394843c9eb60f8ab)
* prereq for 46f5ac2
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>