Multicast computation off by one

A small typo fixup
BTW, how do you like the subject to look like?

cheers,
jamal

[GENL] Multicast computation off by one

When using the first 32 groups, the multicast group to bit mapping
was off by one.

Signed-off-by: Jamal Hadi Salim
Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
diff --git a/genl/genl_utils.h b/genl/genl_utils.h
index 2f2314b..22e9210 100644
--- a/genl/genl_utils.h
+++ b/genl/genl_utils.h
@@ -16,7 +16,7 @@
 /* seems to have dissapeared from netlink.h */
 static inline __u32 nl_mgrp(__u32 group)
 {
-	return group ? 1 << group : 0;
+	return group ? (1 << (group -1)) : 0;
 }
 
 #endif