Add support for 64-bit systems.

Currently, the VTA HW and VTA driver support only 32-bit systems.

The update requires:

• Software updates for address sizes
• Hardware updates for addresses, registers etc

These may already be implemented for Ultra96 and only need to be adapted for RISC-V2TA as well. To be able to deploy on ZCU102 (Ultrascale+), presuming that U-DMA-BUF creates a buffer in the lower area of the memory (such that 32-bits suffice), the following change was implemented in src/riscv2ta/pynq_driver.cc, line 58: vta_phy_addr_t vta_phy_addr = static_cast<vta_phy_addr_t>(reinterpret_cast<uintptr_t>(phy_addr));