net: chelsio: cxgb3: constify attribute_group structures.

attribute_group are not supposed to change at runtime. All functions
working with attribute_group 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
  28720	    985	     12	  29717	   7415	net/.../cxgb3/cxgb3_main.o

File size After adding 'const':
   text	   data	    bss	    dec	    hex	filename
  28848	    857	     12	  29717	   7415	net/.../cxgb3/cxgb3_main.o
Signed-off-by: NArvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/chelsio/cxgb3/cxgb3_main.c

@@ -793,7 +793,9 @@ static struct attribute *cxgb3_attrs[] = {
 	NULL
 };
 
-static struct attribute_group cxgb3_attr_group = {.attrs = cxgb3_attrs };
+static const struct attribute_group cxgb3_attr_group = {
+	.attrs = cxgb3_attrs,
+};
 
 static ssize_t tm_attr_show(struct device *d,
 			    char *buf, int sched)
@@ -880,7 +882,9 @@ static struct attribute *offload_attrs[] = {
 	NULL
 };
 
-static struct attribute_group offload_attr_group = {.attrs = offload_attrs };
+static const struct attribute_group offload_attr_group = {
+	.attrs = offload_attrs,
+};
 
 /*
  * Sends an sk_buff to an offload queue driver