[VME][PCIe] add screw holders for the Samtec connector
The LSHM-120-02.5-L-DV-A-S-K-TR is to be plugged to the cable assembly: HLCD-20-06.00-TRS-TRS-1 https://www.samtec.com/products/hlcd (option with screws), therefore provision for the screwing shall be taken