Function sys_dlist_peek_prev

pub unsafe extern "C" fn sys_dlist_peek_prev(
    list: *mut _dnode,
    node: *mut _dnode,
) -> *mut _dnode

@brief get a reference to the previous item in the list

@param list the doubly-linked list to operate on @param node the node from which to get the previous element in the list

@return a pointer to the previous element from a node, NULL if node is the tail or NULL (when node comes from reading the head of an empty list).