cxgb4: make function ch_flower_stats_cb, fixes warning

The function ch_flower_stats_cb is local to the source and does not need
to be in global scope, so make it static.

Cleans up sparse warnings:
symbol 'ch_flower_stats_cb' was not declared. Should it be static?
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/chelsio/cxgb4/cxgb4_tc_flower.c

@@ -366,7 +366,7 @@ int cxgb4_tc_flower_destroy(struct net_device *dev,
 	return ret;
 }
 
-void ch_flower_stats_cb(unsigned long data)
+static void ch_flower_stats_cb(unsigned long data)
 {
 	struct adapter *adap = (struct adapter *)data;
 	struct ch_tc_flower_entry *flower_entry;