mptcp: move mptcp_pm_gen.h's include

Nothing from protocol.h depends on mptcp_pm_gen.h, only code from
pm_netlink.c and pm_userspace.c depends on it.

So this include can be moved where it is needed to avoid a "unused
includes" warning.

Reviewed-by: Geliang Tang <geliang@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Mat Martineau <martineau@kernel.org>
Link: https://lore.kernel.org/r/20240514011335.176158-8-martineau@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/mptcp/pm_netlink.c

@@ -14,6 +14,7 @@
 
 #include "protocol.h"
 #include "mib.h"
+#include "mptcp_pm_gen.h"
 
 static int pm_nl_pernet_id;
 

net/mptcp/pm_userspace.c

@@ -6,6 +6,7 @@
 
 #include "protocol.h"
 #include "mib.h"
+#include "mptcp_pm_gen.h"
 
 void mptcp_free_local_addr_list(struct mptcp_sock *msk)
 {

net/mptcp/protocol.h

@@ -14,8 +14,6 @@
 #include <net/genetlink.h>
 #include <net/rstreason.h>
 
-#include "mptcp_pm_gen.h"
-
 #define MPTCP_SUPPORTED_VERSION	1
 
 /* MPTCP option bits */