net: ieee802154: constify ieee802154_ops structures

Declare the structure ieee802154_ops as const as it is only passed as an
argument to the function  ieee802154_alloc_hw. This argument is of type
const struct ieee802154_ops *, so ieee80254_ops structures having this
property can be declared as const.
Done using Coccinelle:

@r1 disable optional_qualifier @
identifier i;
position p;
@@
static struct ieee802154_ops i@p = {...};

@ok1@
identifier r1.i;
position p;
expression e1;
@@
ieee802154_alloc_hw(e1,&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 ieee802154_ops  i={...};

@depends on !bad disable optional_qualifier@
identifier r1.i;
@@
+const
struct ieee802154_ops  i;

The before and after size details of the affected files are:

   text	   data	    bss	    dec	    hex	filename
   8669	   1176	     16	   9861	   2685	drivers/net/ieee802154/adf7242.o
   8805	   1048	     16	   9869	   268d	drivers/net/ieee802154/adf7242.o

   text	   data	    bss	    dec	    hex	filename
   7211	   2296	     32	   9539	   2543	drivers/net/ieee802154/atusb.o
   7339	   2160	     32	   9531	   253b	drivers/net/ieee802154/atusb.o

Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Acked-by: Stefan Schmidt <stefan@osg.samsung.com>
Signed-off-by: David S. Miller <davem@davemloft.net>