io_uring: fix io_recvmsg_prep_multishot sparse warnings

Fix casts missing the __user parts. This seemed to only cause errors on
the alpha build, or if checked with sparse, but it was definitely an
oversight.

Reported-by: kernel test robot <lkp@intel.com>
Fixes: 9bb6690 ("io_uring: support multishot in recvmsg")
Signed-off-by: Dylan Yudaken <dylany@fb.com>
Link: https://lore.kernel.org/r/20220805115450.3921352-1-dylany@fb.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: Dylan Yudaken

io_uring/net.c

@@ -576,12 +576,12 @@ static int io_recvmsg_prep_multishot(struct io_async_msghdr *kmsg,
 	if (kmsg->controllen) {
 		unsigned long control = ubuf + hdr - kmsg->controllen;
 
-		kmsg->msg.msg_control_user = (void *) control;
+		kmsg->msg.msg_control_user = (void __user *) control;
 		kmsg->msg.msg_controllen = kmsg->controllen;
 	}
 
 	sr->buf = *buf; /* stash for later copy */
-	*buf = (void *) (ubuf + hdr);
+	*buf = (void __user *) (ubuf + hdr);
 	kmsg->payloadlen = *len = *len - hdr;
 	return 0;
 }