most: core: Constify static attribute_group structs

The only usage of these is to put their addresses in arrays of pointers
to const attribute_groups. Make them const to allow the compiler to put
them in read-only memory.

Signed-off-by: Rikard Falkeborn <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/most/core.c

···
 	NULL,
 };
 
-static struct attribute_group channel_attr_group = {
+static const struct attribute_group channel_attr_group = {
 	.attrs = channel_attrs,
 	.is_visible = channel_attr_is_visible,
 };
···
 	NULL,
 };
 
-static struct attribute_group interface_attr_group = {
+static const struct attribute_group interface_attr_group = {
 	.attrs = interface_attrs,
 };
 
···
 	NULL,
 };
 
-static struct attribute_group mc_attr_group = {
+static const struct attribute_group mc_attr_group = {
 	.attrs = mc_attrs,
 };