Staging: android: ion: constify dma_buf_ops structure

The dma_buf_ops structure is stored in the ops field of a
dma_buf_export_info structure and also used as a condition inside the
if() statement. The if condition does not modify its value and the
ops field is of type const struct *dma_buf_ops, so dma_buf_ops
structures having this property can be declared as const.

File size before:
   text	   data	    bss	    dec	    hex	filename
  14471	    819	    224	  15514	   3c9a
drivers/staging/android/ion/ion.o

File size after:
   text	   data	    bss	    dec	    hex	filename
  14599	    707	    224	  15530	   3caa
drivers/staging/android/ion/ion.o
Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Acked-by: Julia Lawall <julia.lawall@lip6.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/android/ion/ion.c

@@ -1013,7 +1013,7 @@ static int ion_dma_buf_end_cpu_access(struct dma_buf *dmabuf,
 	return 0;
 }
 
-static struct dma_buf_ops dma_buf_ops = {
+static const struct dma_buf_ops dma_buf_ops = {
 	.map_dma_buf = ion_map_dma_buf,
 	.unmap_dma_buf = ion_unmap_dma_buf,
 	.mmap = ion_mmap,