dma-buf: fix htmldocs error for dma_buf_attach_revocable

linux-next testing showed this htmldoc error due to a missing extra
line in the comments; add it.

Fixes: be6d4c9 ("dma-buf: Add dma_buf_attach_revocable()")
Reported-by: Mark Brown <[email protected]>
Closes: https://lore.kernel.org/lkml/[email protected]/
Signed-off-by: Sumit Semwal <[email protected]>
Reviewed-by: Christian König <[email protected]>
Link: https://patch.msgid.link/[email protected]

Author: sumitsemwal

drivers/dma-buf/dma-buf.c

@@ -1353,6 +1353,7 @@ EXPORT_SYMBOL_NS_GPL(dma_buf_attach_revocable, "DMA_BUF");
  * Upon return importers may continue to access the DMA-buf memory. The caller
  * must do two additional waits to ensure that the memory is no longer being
  * accessed:
+ *
  *  1) Until dma_resv_wait_timeout() retires fences the importer is allowed to
  *     fully access the memory.
  *  2) Until the importer calls unmap it is allowed to speculatively