net: make xps_needed and xps_rxqs_needed static

Since their introduction in commit 04157469 ("net: Use static_key
for XPS maps"), xps_needed and xps_rxqs_needed were never used outside
net/core/dev.c, so I don't really understand why they were exported as
symbols in the first place.

This is needed in order to silence a "make W=1" warning about these
static keys not being declared as static variables, but not having a
previous declaration in a header file nonetheless.

Cc: Amritha Nambiar <amritha.nambiar@intel.com>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/dev.c

@@ -2451,10 +2451,8 @@ int netdev_txq_to_tc(struct net_device *dev, unsigned int txq)
 EXPORT_SYMBOL(netdev_txq_to_tc);
 
 #ifdef CONFIG_XPS
-struct static_key xps_needed __read_mostly;
-EXPORT_SYMBOL(xps_needed);
-struct static_key xps_rxqs_needed __read_mostly;
-EXPORT_SYMBOL(xps_rxqs_needed);
+static struct static_key xps_needed __read_mostly;
+static struct static_key xps_rxqs_needed __read_mostly;
 static DEFINE_MUTEX(xps_map_mutex);
 #define xmap_dereference(P)		\
 	rcu_dereference_protected((P), lockdep_is_held(&xps_map_mutex))