riscv: qemu: Add platform-specific Kconfig options

Add the QEMU RISC-V platform-specific Kconfig options, to include
CPU and timer drivers.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Lukas Auer <lukas.auer@aisec.fraunhofer.de>
Reviewed-by: Anup Patel <anup@brainfault.org>
3 files changed