dma-buf: Remove leftover [un]map_atomic comments

The map_atomic/unmap_atomic callbacks have been removed, remove
the related comments.

Fixes: f664a526 ("dma-buf: remove kmap_atomic interface")
Signed-off-by: NAndrew F. Davis <afd@ti.com>
Signed-off-by: NSumit Semwal <sumit.semwal@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190321200957.16938-1-afd@ti.com

include/linux/dma-buf.h

@@ -39,11 +39,6 @@ struct dma_buf_attachment;
 
 /**
  * struct dma_buf_ops - operations possible on struct dma_buf
- * @map_atomic: [optional] maps a page from the buffer into kernel address
- *		space, users may not block until the subsequent unmap call.
- *		This callback must not sleep.
- * @unmap_atomic: [optional] unmaps a atomically mapped page from the buffer.
- *		  This Callback must not sleep.
  * @map: [optional] maps a page from the buffer into kernel address space.
  * @unmap: [optional] unmaps a page from the buffer.
  * @vmap: [optional] creates a virtual mapping for the buffer into kernel