include: Extend struct sbi_trap_info for mtval2 and mtinst

We have two new trap CSRs namely mtval2 and mtinst when
RISC-V hypervisor extension is available hence we extend
struct sbi_trap_info accordingly.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>