riscv: Add SBI v0.2 extension definitions

Few v0.1 SBI calls are being replaced by new SBI calls that follows
v0.2 calling convention.

This patch just defines these new extensions.

This commit is inspired from Linux kernel patch:
https://patchwork.kernel.org/patch/11407359/



Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Pragnesh Patel <pragnesh.patel@sifive.com>