dma-buf: Fix kerneldoc of dma_buf_set_name()

Fix W=1 compile warnings (invalid kerneldoc):

    drivers/dma-buf/dma-buf.c:328: warning: Function parameter or member 'dmabuf' not described in 'dma_buf_set_name'
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200819175134.19261-1-krzk@kernel.org

drivers/dma-buf/dma-buf.c

@@ -316,7 +316,7 @@ static __poll_t dma_buf_poll(struct file *file, poll_table *poll)
  * name of the dma-buf if the same piece of memory is used for multiple
  * purpose between different devices.
  *
- * @dmabuf [in]     dmabuf buffer that will be renamed.
+ * @dmabuf: [in]     dmabuf buffer that will be renamed.
  * @buf:    [in]     A piece of userspace memory that contains the name of
  *                   the dma-buf.
  *