dma-fence: remove duplicate word in comment

Signed-off-by: NFrank Binns <frank.binns@imgtec.com>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/1508333423-5394-1-git-send-email-frank.binns@imgtec.com

include/linux/dma-fence.h

@@ -128,7 +128,7 @@ struct dma_fence_cb {
  * implementation know that there is another driver waiting on
  * the signal (ie. hw->sw case).
  *
- * This function can be called called from atomic context, but not
+ * This function can be called from atomic context, but not
  * from irq context, so normal spinlocks can be used.
  *
  * A return value of false indicates the fence already passed,