ubus: Correct usage of timeout on poll function

As the man page explains:

"Specifying a timeout of zero causes poll() to return immediately,
even if no file descriptors are ready."

The use of 0 as timeout could cause libubus to busy loop if the
socket was non-blocking. For blocking sockets, this was less
apparent as the subsequent read() would then block.

Signed-off-by: Karl Vogel <karl.vogel@gmail.com>

libubus-io.c

@@ -54,7 +54,7 @@ static void wait_data(int fd, bool write)
 	struct pollfd pfd = { .fd = fd };
 
 	pfd.events = write ? POLLOUT : POLLIN;
-	poll(&pfd, 1, 0);
+	poll(&pfd, 1, -1);
 }
 
 static int writev_retry(int fd, struct iovec *iov, int iov_len, int sock_fd)
@@ -321,7 +321,7 @@ void __hidden ubus_poll_data(struct ubus_context *ctx, int timeout)
 		.events = POLLIN | POLLERR,
 	};
 
-	poll(&pfd, 1, timeout);
+	poll(&pfd, 1, timeout ? timeout : -1);
 	ubus_handle_data(&ctx->sock, ULOOP_READ);
 }