net: bridge: 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
2645 896 0 3541 dd5 net/bridge/br_sysfs_br.o

File size After adding 'const':
text data bss dec hex filename
2701 832 0 3533 dcd net/bridge/br_sysfs_br.o

Signed-off-by: Arvind Yadav <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/bridge/br_sysfs_br.c

···
 	NULL
 };
 
-static struct attribute_group bridge_group = {
+static const struct attribute_group bridge_group = {
 	.name = SYSFS_BRIDGE_ATTR,
 	.attrs = bridge_attrs,
 };