lib/list: Add list_append

This method will add a node to the end of the list.

BUG=b:179699789
TEST=Boot guybrush to the OS

Signed-off-by: Raul E Rangel <rrangel@chromium.org>
Change-Id: I1792e40f789e3ef16ceca65ce4cae946e08583d1
Reviewed-on: https://review.coreboot.org/c/coreboot/+/58805
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>

src/include/list.h

@@ -15,6 +15,8 @@ void list_remove(struct list_node *node);
 void list_insert_after(struct list_node *node, struct list_node *after);
 // Insert list_node node before list_node before in a doubly linked list.
 void list_insert_before(struct list_node *node, struct list_node *before);
+// Appends the node to the end of the list.
+void list_append(struct list_node *node, struct list_node *head);
 
 #define list_for_each(ptr, head, member)                                      \
 	for ((ptr) = container_of((head).next, typeof(*(ptr)), member);       \