Given the head of a linked list and an integer val, remove all the nodes of the linked list that has Node.val == val, and return the new head.
Input: head = [1,2,6,3,4,5,6], val = 6
Output: [1,2,3,4,5]
Input: head = [], val = 1
Output: []
Input: head = [7,7,7,7], val = 7
Output: []