netfilter: xtables: untangle spaghetti if clauses in checkentry

As I'm changing the return values soon, I want to have a clear visual
path.

Signed-off-by: Jan Engelhardt <jengelh@medozas.de>
diff --git a/net/netfilter/xt_dccp.c b/net/netfilter/xt_dccp.c
index 0989f29a..8f6014f 100644
--- a/net/netfilter/xt_dccp.c
+++ b/net/netfilter/xt_dccp.c
@@ -127,9 +127,13 @@
 {
 	const struct xt_dccp_info *info = par->matchinfo;
 
-	return !(info->flags & ~XT_DCCP_VALID_FLAGS)
-		&& !(info->invflags & ~XT_DCCP_VALID_FLAGS)
-		&& !(info->invflags & ~info->flags);
+	if (info->flags & ~XT_DCCP_VALID_FLAGS)
+		return false;
+	if (info->invflags & ~XT_DCCP_VALID_FLAGS)
+		return false;
+	if (info->invflags & ~info->flags)
+		return false;
+	return true;
 }
 
 static struct xt_match dccp_mt_reg[] __read_mostly = {