s390x/css: Allocate channel_subsys statically

s390x/css: Allocate channel_subsys statically

There's no need to use g_malloc0() to allocate the channel_subsys
struct, just use a static variable.

Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Alexander Graf <agraf@suse.de>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Message-Id: <1455656347-29033-3-git-send-email-ehabkost@redhat.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
[adapted on top of indicator changes]
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>