iio: light: apds9960: constify attribute_group structures

Check for attribute_group structures that are only stored in the
attrs filed of iio_info structure. As the attrs field of iio_info
structures is constant, so these attribute_group structures can also be
declared constant.
Done using coccinelle:

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

@ok1@
identifier r1.i;
position p;
struct iio_info x;
@@
x.attrs=&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 attribute_group i={...};

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

File size before:
   text	   data	    bss	    dec	    hex	filename
   8503	    488	      0	   8991	   231f	drivers/iio/light/apds9960.o

File size after:
   text	   data	    bss	    dec	    hex	filename
   8567	    424	      0	   8991	   231f	drivers/iio/light/apds9960.o
Signed-off-by: simran singhal <singhalsimran0@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/light/apds9960.c

@@ -343,7 +343,7 @@ static struct attribute *apds9960_attributes[] = {
 	NULL,
 };
 
-static struct attribute_group apds9960_attribute_group = {
+static const struct attribute_group apds9960_attribute_group = {
 	.attrs = apds9960_attributes,
 };