netfilter: xtables: change targets to return error code

Part of the transition of done by this semantic patch:
// <smpl>
@ rule1 @
struct xt_target ops;
identifier check;
@@
 ops.checkentry = check;

@@
identifier rule1.check;
@@
 check(...) { <...
-return true;
+return 0;
 ...> }

@@
identifier rule1.check;
@@
 check(...) { <...
-return false;
+return -EINVAL;
 ...> }
// </smpl>

Signed-off-by: Jan Engelhardt <jengelh@medozas.de>
diff --git a/net/netfilter/xt_NFLOG.c b/net/netfilter/xt_NFLOG.c
index 13e6c00..42dd874 100644
--- a/net/netfilter/xt_NFLOG.c
+++ b/net/netfilter/xt_NFLOG.c
@@ -42,10 +42,10 @@
 	const struct xt_nflog_info *info = par->targinfo;
 
 	if (info->flags & ~XT_NFLOG_MASK)
-		return false;
+		return -EINVAL;
 	if (info->prefix[sizeof(info->prefix) - 1] != '\0')
-		return false;
-	return true;
+		return -EINVAL;
+	return 0;
 }
 
 static struct xt_target nflog_tg_reg __read_mostly = {