driver model: constify attribute groups

Let attribute group vectors be declared "const".  We'd
like to let most attribute metadata live in read-only
sections... this is a start.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/firewire/core-device.c b/drivers/firewire/core-device.c
index 97e656a..9d0dfcb 100644
--- a/drivers/firewire/core-device.c
+++ b/drivers/firewire/core-device.c
@@ -312,7 +312,7 @@
 	group->groups[0] = &group->group;
 	group->groups[1] = NULL;
 	group->group.attrs = group->attrs;
-	dev->groups = group->groups;
+	dev->groups = (const struct attribute_group **) group->groups;
 }
 
 static ssize_t modalias_show(struct device *dev,