lib: sbi_trap: Save mstatus[h].GVA in trap->gva

The machine mode GVA field is available if the hypervisor extension is
implemented, and indicates if mtval is a guest virtual address. Add a
gva field to sbi_trap_info for this, and in __sbi_expected_trap_hext,
save mstatus[h].GVA to it, so that gva indicates if tval is a guest
virtual address. If the hypervisor extension is not implemented, always
set gva to 0.

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