lib: sbi_trap: Set hypervisor CSRs for HS-mode

The hypervisor CSRs hstatus, htval, htinst should always be set if the
trap is to be taken in HS-mode, regardless of which mode it came from.

Signed-off-by: Vivian Wang <dramforever@live.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>