NFC: The NFC genl family structure should not be exposed globally

The variable 'nfc_genl_family' is only referenced in this file and
should be marked static to prevent it from being exposed globally.

Quites the sparse warning:

warning: symbol 'nfc_genl_family' was not declared. Should it be static?

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/netlink.c

···
 	.name = NFC_GENL_MCAST_EVENT_NAME,
 };
 
-struct genl_family nfc_genl_family = {
+static struct genl_family nfc_genl_family = {
 	.id = GENL_ID_GENERATE,
 	.hdrsize = 0,
 	.name = NFC_GENL_NAME,