dma-buf: Update obsoluted comments on dma_buf_vmap/vunmap()

A comment for the dma_buf_vmap/vunmap() is not catching up a
corresponding implementation.
Signed-off-by: Shunsuke Mie <mie@igel.co.jp>
Link: https://patchwork.freedesktop.org/patch/msgid/20211008112009.118996-1-mie@igel.co.jpReviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Christian König <christian.koenig@amd.com>

drivers/dma-buf/dma-buf.c

@@ -1052,8 +1052,8 @@ EXPORT_SYMBOL_GPL(dma_buf_move_notify);
  *
  *   Interfaces::
  *
- *      void \*dma_buf_vmap(struct dma_buf \*dmabuf)
- *      void dma_buf_vunmap(struct dma_buf \*dmabuf, void \*vaddr)
+ *      void \*dma_buf_vmap(struct dma_buf \*dmabuf, struct dma_buf_map \*map)
+ *      void dma_buf_vunmap(struct dma_buf \*dmabuf, struct dma_buf_map \*map)
  *
  *   The vmap call can fail if there is no vmap support in the exporter, or if
  *   it runs out of vmalloc space. Note that the dma-buf layer keeps a reference