KVM: s390: fix compile with !CONFIG_COMPAT

arch/s390/kvm/priv.c should include both
linux/compat.h and asm/compat.h.
Fixes this one:

In file included from arch/s390/kvm/priv.c:23:0:
arch/s390/include/asm/compat.h: In function ‘arch_compat_alloc_user_space’:
arch/s390/include/asm/compat.h:258:2: error: implicit declaration of function ‘is_compat_task’
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>

arch/s390/kvm/priv.c

@@ -14,6 +14,7 @@
 #include <linux/kvm.h>
 #include <linux/gfp.h>
 #include <linux/errno.h>
+#include <linux/compat.h>
 #include <asm/asm-offsets.h>
 #include <asm/current.h>
 #include <asm/debug.h>