Documentation/dma-buf-sharing.txt: update API descriptions

Update some descriptions for API arguments and descriptions.
Signed-off-by: Gioh Kim <gioh.kim@lge.com>
Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>

Documentation/dma-buf-sharing.txt

@@ -56,10 +56,10 @@ The dma_buf buffer sharing API usage contains the following steps:
 				     size_t size, int flags,
 				     const char *exp_name)
 
-   If this succeeds, dma_buf_export allocates a dma_buf structure, and returns a
-   pointer to the same. It also associates an anonymous file with this buffer,
-   so it can be exported. On failure to allocate the dma_buf object, it returns
-   NULL.
+   If this succeeds, dma_buf_export_named allocates a dma_buf structure, and
+   returns a pointer to the same. It also associates an anonymous file with this
+   buffer, so it can be exported. On failure to allocate the dma_buf object,
+   it returns NULL.
 
    'exp_name' is the name of exporter - to facilitate information while
    debugging.
@@ -76,7 +76,7 @@ The dma_buf buffer sharing API usage contains the following steps:
    drivers and/or processes.
 
    Interface:
-      int dma_buf_fd(struct dma_buf *dmabuf)
+      int dma_buf_fd(struct dma_buf *dmabuf, int flags)
 
    This API installs an fd for the anonymous file associated with this buffer;
    returns either 'fd', or error.
@@ -157,7 +157,9 @@ to request use of buffer for allocation.
    "dma_buf->ops->" indirection from the users of this interface.
 
    In struct dma_buf_ops, unmap_dma_buf is defined as
-      void (*unmap_dma_buf)(struct dma_buf_attachment *, struct sg_table *);
+      void (*unmap_dma_buf)(struct dma_buf_attachment *,
+                            struct sg_table *,
+                            enum dma_data_direction);
 
    unmap_dma_buf signifies the end-of-DMA for the attachment provided. Like
    map_dma_buf, this API also must be implemented by the exporter.