io_uring/kbuf: move io_ring_head_to_buf() to kbuf.h

In preparation for using this helper in kbuf.h as well, move it there and
turn it into a macro.
Signed-off-by: Jens Axboe <axboe@kernel.dk>

io_uring/kbuf.c

@@ -132,12 +132,6 @@ static int io_provided_buffers_select(struct io_kiocb *req, size_t *len,
 	return 0;
 }
 
-static struct io_uring_buf *io_ring_head_to_buf(struct io_uring_buf_ring *br,
-						__u16 head, __u16 mask)
-{
-	return &br->bufs[head & mask];
-}
-
 static void __user *io_ring_buffer_select(struct io_kiocb *req, size_t *len,
 					  struct io_buffer_list *bl,
 					  unsigned int issue_flags)

io_uring/kbuf.h

@@ -121,6 +121,9 @@ static inline bool io_kbuf_recycle(struct io_kiocb *req, unsigned issue_flags)
 	return false;
 }
 
+/* Mapped buffer ring, return io_uring_buf from head */
+#define io_ring_head_to_buf(br, head, mask)	&(br)->bufs[(head) & (mask)]
+
 static inline void io_kbuf_commit(struct io_kiocb *req,
 				  struct io_buffer_list *bl, int nr)
 {