KVM: add missing void __user * cast to access_ok() call

fa3d315a "KVM: Validate userspace_addr of memslot when registered" introduced
this new warning onn s390:

kvm_main.c: In function '__kvm_set_memory_region':
kvm_main.c:654:7: warning: passing argument 1 of '__access_ok' makes pointer from integer without a cast
arch/s390/include/asm/uaccess.h:53:19: note: expected 'const void *' but argument is of type '__u64'

Add the missing cast to get rid of it again...

Cc: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

virt/kvm/kvm_main.c

@@ -651,7 +651,9 @@ int __kvm_set_memory_region(struct kvm *kvm,
 	/* We can read the guest memory with __xxx_user() later on. */
 	if (user_alloc &&
 	    ((mem->userspace_addr & (PAGE_SIZE - 1)) ||
-	     !access_ok(VERIFY_WRITE, mem->userspace_addr, mem->memory_size)))
+	     !access_ok(VERIFY_WRITE,
+			(void __user *)(unsigned long)mem->userspace_addr,
+			mem->memory_size)))
 		goto out;
 	if (mem->slot >= KVM_MEMORY_SLOTS + KVM_PRIVATE_MEM_SLOTS)
 		goto out;