IB/hfi1: constify mmu_notifier_ops structure

Declare the structure mmu_notifier_ops as const as it is only stored in
the ops field of a mmu_notifier structure. The ops field is of type
const struct mmu_notifier_ops *, so mmu_notifier_ops structures having
this property can be declared as const.
Done using coccinelle:
@r1 disable optional_qualifier @
identifier i;
position p;
@@
static struct mmu_notifier_ops i@p = {...};

@ok1@
identifier r1.i;
position p;
struct mmu_rb_handler handler;
@@
handler.mn.ops=&i@p

@bad@
position p!={r1.p,ok1.p};
identifier r1.i;
@@
i@p

@depends on !bad disable optional_qualifier@
identifier r1.i;
@@
static
+const
struct mmu_notifier_ops i={...};

@depends on !bad disable optional_qualifier@
identifier r1.i;
@@
+const
struct mmu_notifier_ops i;

File size before:
   text	   data	    bss	    dec	    hex	filename
   3566	     72	     16	   3654	    e46
drivers/infiniband/hw/hfi1/mmu_rb.o

File size after:
   text	   data	    bss	    dec	    hex	filename
   3658	      0	     16	   3674	    e5a
drivers/infiniband/hw/hfi1/mmu_rb.o

Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>