NFC: Quiet nci/ntf.c sparse noise about plain integer as NULL pointer

Pointers should be cleared with NULL, not 0.

Quiets a couple sparse warnings of the type:

warning: Using plain integer as NULL pointer
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Lauro Ramos Venancio <lauro.venancio@openbossa.org>
Cc: Aloisio Almeida Jr <aloisio.almeida@openbossa.org>
Cc: Samuel Ortiz <sameo@linux.intel.com>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/nfc/nci/ntf.c

@@ -497,7 +497,7 @@ static void nci_rf_deactivate_ntf_packet(struct nci_dev *ndev,
 	/* drop partial rx data packet */
 	if (ndev->rx_data_reassembly) {
 		kfree_skb(ndev->rx_data_reassembly);
-		ndev->rx_data_reassembly = 0;
+		ndev->rx_data_reassembly = NULL;
 	}
 
 	/* complete the data exchange transaction, if exists */