NFC: Fix sparse warnings due to missing static

Signed-off-by: Arron Wang <arron.wang@intel.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
diff --git a/drivers/nfc/pn544/pn544.c b/drivers/nfc/pn544/pn544.c
index cf34445..cc666de 100644
--- a/drivers/nfc/pn544/pn544.c
+++ b/drivers/nfc/pn544/pn544.c
@@ -714,8 +714,8 @@
 	return 0;
 }
 
-void pn544_hci_event_received(struct nfc_hci_dev *hdev, u8 gate, u8 event,
-				struct sk_buff *skb)
+static void pn544_hci_event_received(struct nfc_hci_dev *hdev, u8 gate,
+					u8 event, struct sk_buff *skb)
 {
 	struct sk_buff *rgb_skb = NULL;
 	int r = 0;