util: add back public poll_read_buf() function (#3079)

This was accidentally removed in #3064.

tokio-util/src/io/mod.rs

@@ -13,3 +13,4 @@ mod stream_reader;
 pub use self::read_buf::read_buf;
 pub use self::reader_stream::ReaderStream;
 pub use self::stream_reader::StreamReader;
+pub use crate::util::poll_read_buf;

tokio-util/src/io/read_buf.rs

@@ -59,7 +59,7 @@ where
 
         fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
             let this = &mut *self;
-            crate::util::poll_read_buf(cx, Pin::new(this.0), this.1)
+            crate::util::poll_read_buf(Pin::new(this.0), cx, this.1)
         }
     }
 }

tokio-util/src/io/reader_stream.rs

@@ -83,7 +83,7 @@ impl<R: AsyncRead> Stream for ReaderStream<R> {
             this.buf.reserve(CAPACITY);
         }
 
-        match poll_read_buf(cx, reader, &mut this.buf) {
+        match poll_read_buf(reader, cx, &mut this.buf) {
             Poll::Pending => Poll::Pending,
             Poll::Ready(Err(err)) => {
                 self.project().reader.set(None);