drivers/net/wireless: fix sparse warnings: make symbols static

Fix this sparse warnings:

  drivers/net/wireless/airo.c:3610:6: warning: symbol 'mpi_receive_802_11' was not declared. Should it be static?
  drivers/net/wireless/atmel.c:3183:6: warning: symbol 'atmel_join_bss' was not declared. Should it be static?
  drivers/net/wireless/ray_cs.c:831:5: warning: symbol 'ray_dev_init' was not declared. Should it be static?

Signed-off-by: Hannes Eder <hannes@hanneseder.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/wireless/airo.c b/drivers/net/wireless/airo.c
index 67d504e..fc4322c 100644
--- a/drivers/net/wireless/airo.c
+++ b/drivers/net/wireless/airo.c
@@ -3607,7 +3607,7 @@
 	}
 }
 
-void mpi_receive_802_11 (struct airo_info *ai)
+static void mpi_receive_802_11(struct airo_info *ai)
 {
 	RxFid rxd;
 	struct sk_buff *skb = NULL;