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 <[e-mail]>
Cc: Lauro Ramos Venancio <[e-mail]>
Cc: Aloisio Almeida Jr <[e-mail]>
Cc: Samuel Ortiz <[e-mail]>
Cc: "David S. Miller" <[e-mail]>
Signed-off-by: Samuel Ortiz <[e-mail]>
Signed-off-by: John W. Linville <[e-mail]>

net/nfc/nci/ntf.c

···
 	/* 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 */