util: remove const specifier from nlmsghdr arg to virNetlinkDumpCallback()

This is problematic if a callback function wants to send the nlmsghdr
to a library function that has no "const" in its prototype
(e.g. nlmsg_find_attr())
Signed-off-by: NLaine Stump <laine@laine.org>
Reviewed-by: NErik Skultety <eskultet@redhat.com>

src/util/virnetdevip.c

@@ -506,7 +506,7 @@ struct virNetDevIPCheckIPv6ForwardingData {
 };
 
 static int
-virNetDevIPCheckIPv6ForwardingCallback(const struct nlmsghdr *resp,
+virNetDevIPCheckIPv6ForwardingCallback(struct nlmsghdr *resp,
                                        void *opaque)
 {
     struct rtmsg *rtmsg = NLMSG_DATA(resp);

src/util/virnetlink.h

@@ -79,7 +79,7 @@ int virNetlinkCommand(struct nl_msg *nl_msg,
                       uint32_t src_pid, uint32_t dst_pid,
                       unsigned int protocol, unsigned int groups);
 
-typedef int (*virNetlinkDumpCallback)(const struct nlmsghdr *resp,
+typedef int (*virNetlinkDumpCallback)(struct nlmsghdr *resp,
                                       void *data);
 
 int virNetlinkDumpCommand(struct nl_msg *nl_msg,