usb: usbtmc: 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.
Signed-off-by: NArvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/class/usbtmc.c

@@ -1085,7 +1085,7 @@ static struct attribute *capability_attrs[] = {
 	NULL,
 };
 
-static struct attribute_group capability_attr_grp = {
+static const struct attribute_group capability_attr_grp = {
 	.attrs = capability_attrs,
 };
 
@@ -1151,7 +1151,7 @@ static struct attribute *data_attrs[] = {
 	NULL,
 };
 
-static struct attribute_group data_attr_grp = {
+static const struct attribute_group data_attr_grp = {
 	.attrs = data_attrs,
 };