Input: constify attribute_group structures

attribute_groups are not supposed to change at runtime. All functions
working with attribute_groups provided by <linux/sysfs.h> work with const
attribute_group. So mark the non-const structs as const.

File size before:
   text	   data	    bss	    dec	    hex	filename
  17755	   1312	     16	  19083	   4a8b	drivers/input/input.o

File size After adding 'const':
   text	   data	    bss	    dec	    hex	filename
  17947	   1120	     16	  19083	   4a8b	drivers/input/input.o
Signed-off-by: NArvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: NDmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/input.c

@@ -1398,7 +1398,7 @@ static struct attribute *input_dev_attrs[] = {
 	NULL
 };
 
-static struct attribute_group input_dev_attr_group = {
+static const struct attribute_group input_dev_attr_group = {
 	.attrs	= input_dev_attrs,
 };
 
@@ -1425,7 +1425,7 @@ static struct attribute *input_dev_id_attrs[] = {
 	NULL
 };
 
-static struct attribute_group input_dev_id_attr_group = {
+static const struct attribute_group input_dev_id_attr_group = {
 	.name	= "id",
 	.attrs	= input_dev_id_attrs,
 };
@@ -1495,7 +1495,7 @@ static struct attribute *input_dev_caps_attrs[] = {
 	NULL
 };
 
-static struct attribute_group input_dev_caps_attr_group = {
+static const struct attribute_group input_dev_caps_attr_group = {
 	.name	= "capabilities",
 	.attrs	= input_dev_caps_attrs,
 };