RDMA/uverbs: Add a __user annotation to a pointer

This patch avoids that sparse and smatch report the following:

  warning: cast removes address space of expression
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Fixes: 3a6532c9 ("RDMA/uverbs: Use uverbs_attr_bundle to pass udata for write")
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/core/uverbs_main.c

@@ -720,7 +720,7 @@ static ssize_t ib_uverbs_write(struct file *filp, const char __user *buf,
 			 * then the command request structure starts
 			 * with a '__aligned u64 response' member.
 			 */
-			ret = get_user(response, (const u64 *)buf);
+			ret = get_user(response, (const u64 __user *)buf);
 			if (ret)
 				goto out_unlock;