drm: Fix up kerneldoc for new drm_gem_dmabuf_export()

I hit send before completing a make htmldoc, and lo I forgot to fix up
the cut'n'paste.

Fixes: a4fce9cb782a ("drm/prime: Take a ref on the drm_dev when exporting...")
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20161005174056.29869-1-chris@chris-wilson.co.uk

drivers/gpu/drm/drm_prime.c

@@ -285,7 +285,8 @@ static void drm_gem_unmap_dma_buf(struct dma_buf_attachment *attach,
 
 /**
  * drm_gem_dmabuf_export - dma_buf export implementation for GEM
- * @dma_buf: buffer to be exported
+ * @dev: parent device for the exported dmabuf
+ * @exp_info: the export information used by dma_buf_export()
  *
  * This wraps dma_buf_export() for use by generic GEM drivers that are using
  * drm_gem_dmabuf_release(). In addition to calling dma_buf_export(), we take