iio: humidity: hdc100x: 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
   3459	    488	      0	   3947	    f6b	drivers/iio/humidity/hdc100x.o

File size after:
   text	   data	    bss	    dec	    hex	filename
   3507	    424	      0	   3931	    f5b	drivers/iio/humidity/hdc100x.o
Signed-off-by: simran singhal <singhalsimran0@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/humidity/hdc100x.c

@@ -79,7 +79,7 @@ static struct attribute *hdc100x_attributes[] = {
 	NULL
 };
 
-static struct attribute_group hdc100x_attribute_group = {
+static const struct attribute_group hdc100x_attribute_group = {
 	.attrs = hdc100x_attributes,
 };