ath9k: constify ath_bus_ops structure

Declare the structure ath_bus_ops as const as it is only passed as an
argument to the function ath9k_init_device. This argument is of type
const struct ath_bus_ops *, so ath_bus_ops structures with this property
can be declared as const.
Done using Coccinelle:
@r1 disable optional_qualifier @
identifier i;
position p;
@@
static struct ath_bus_ops i@p = {...};

@ok1@
identifier r1.i;
position p;
expression e1,e2;
@@
ath9k_init_device(e1,e2,&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 ath_bus_ops i={...};

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

File size before:
   text	   data	    bss	    dec	    hex	filename
   1295	    232	      0	   1527	    5f7	ath/ath9k/ahb.o

File size after:
   text	   data	    bss	    dec	    hex	filename
   1359	    176	      0	   1535	    5ff	ath/ath9k/ahb.o

Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>

drivers/net/wireless/ath/ath9k/ahb.c

@@ -62,7 +62,7 @@ static bool ath_ahb_eeprom_read(struct ath_common *common, u32 off, u16 *data)
 	return false;
 }
 
-static struct ath_bus_ops ath_ahb_bus_ops  = {
+static const struct ath_bus_ops ath_ahb_bus_ops  = {
 	.ath_bus_type = ATH_AHB,
 	.read_cachesize = ath_ahb_read_cachesize,
 	.eeprom_read = ath_ahb_eeprom_read,