forked from Mirrors/opensbi

Attempting to access the menvcfg CSR raises an illegal instruction
exception on hardware which implements Sm1p11 or older.
Fixes: e9ee9678ba
("lib: sbi: fwft: add support for SBI_FWFT_PTE_AD_HW_UPDATING")
Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
Reviewed-by: Anup Patel <anup@brainfault.org>