nfc: fix error handling of nfc_proto_register()

When nfc proto id is using, nfc_proto_register() return -EBUSY error
code, but forgot to unregister proto. Fix it by adding proto_unregister()
in the error handling case.

Fixes: c7fe3b52 ("NFC: add NFC socket family")
Signed-off-by: NZiyang Xuan <william.xuanziyang@huawei.com>
Reviewed-by: NKrzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Link: https://lore.kernel.org/r/20211013034932.2833737-1-william.xuanziyang@huawei.comSigned-off-by: NJakub Kicinski <kuba@kernel.org>

net/nfc/af_nfc.c

@@ -60,6 +60,9 @@ int nfc_proto_register(const struct nfc_protocol *nfc_proto)
 		proto_tab[nfc_proto->id] = nfc_proto;
 	write_unlock(&proto_tab_lock);
 
+	if (rc)
+		proto_unregister(nfc_proto->proto);
+
 	return rc;
 }
 EXPORT_SYMBOL(nfc_proto_register);