WIP: libpayload: add initial support for RISC-V

Parse fdt provided by a2 and extract coreboot tables from it.

Change-Id: I91df02069a0f8fd8771f73de0e866e9cea05cded
Signed-off-by: Philipp Hug <philipp@hug.cx>
---
M payloads/libpayload/Kconfig
M payloads/libpayload/Makefile
M payloads/libpayload/Makefile.inc
A payloads/libpayload/arch/riscv/Kconfig
A payloads/libpayload/arch/riscv/Makefile.inc
A payloads/libpayload/arch/riscv/coreboot.c
A payloads/libpayload/arch/riscv/head.S
A payloads/libpayload/arch/riscv/libpayload.ldscript
A payloads/libpayload/arch/riscv/main.c
A payloads/libpayload/arch/riscv/sysinfo.c
A payloads/libpayload/arch/riscv/timer.c
A payloads/libpayload/arch/riscv/util.S
A payloads/libpayload/arch/riscv/virtual.c
M payloads/libpayload/bin/lpgcc
A payloads/libpayload/configs/config.riscv
A payloads/libpayload/configs/defconfig-riscv
A payloads/libpayload/include/riscv/arch/asm.h
A payloads/libpayload/include/riscv/arch/io.h
A payloads/libpayload/include/riscv/arch/types.h
A payloads/libpayload/include/riscv/arch/virtual.h
20 files changed, 947 insertions(+), 1 deletion(-)