Drop unreachable OOM branches

Since commit 40faacb ("Check memory allocation") memory allocations use
a wrapper that checks internally for OOM.  Remove the unreachable
branches at caller sites.

src/parse_functions.c

@@ -803,9 +803,6 @@ static enum node_flavor attr_to_node_flavor(enum attr_flavor flavor)
 static enum selint_error insert_attribute(struct policy_node **cur, enum attr_flavor flavor, const char *type, struct string_list *attrs, unsigned int lineno)
 {
 	struct attribute_data *data = xcalloc(1, sizeof(struct attribute_data));
-	if (!data) {
-		return SELINT_OUT_OF_MEM;
-	}
 	union node_data nd;
 	nd.at_data = data;
 

src/tree.c

@@ -32,10 +32,6 @@ enum selint_error insert_policy_node_child(struct policy_node *parent,
 	}
 
 	struct policy_node *to_insert = xmalloc(sizeof(struct policy_node));
-	if (!to_insert) {
-		return SELINT_OUT_OF_MEM;
-	}
-
 	to_insert->parent = parent;
 	to_insert->next = NULL;
 	to_insert->first_child = NULL;
@@ -73,9 +69,6 @@ enum selint_error insert_policy_node_next(struct policy_node *prev,
 	}
 
 	struct policy_node *to_insert = xmalloc(sizeof(struct policy_node));
-	if (!to_insert) {
-		return SELINT_OUT_OF_MEM;
-	}
 
 	prev->next = to_insert;