Add support for Xpulp related extensions

Created by: liweiwei90

Based on instruction_set_extensions spec in cv32e40p

Xpulp extensions can be enabled by adding parameter "-cpu rv32,xcvalu=true,xcvbi=true,xcvbitmanip=true,xcvhwlp=true,xcvmac=true,xcvmem=true,xcvsimd=true" to qemu-riscv32 or qemu-system-riscv32, such as we can run riscv32 application by

qemu-riscv32  -cpu rv32,xcvalu=true,xcvbi=true,xcvbitmanip=true,xcvhwlp=true,xcvmac=true,xcvmem=true,xcvsimd=true  
<path-to-app>