riscv: Add sfence.vma after early page table changes

riscv: Add sfence.vma after early page table changes

[ Upstream commit 21190b74bcf3a36ebab9a715088c29f59877e1f3 ]

This invalidates local TLB after modifying the page tables during early init as
it's too early to handle suprious faults as we otherwise do.

Fixes: f2c17aabc917 ("RISC-V: Implement compile-time fixed mappings")
Reported-by: Syven Wang <syven.wang@sifive.com>
Signed-off-by: Syven Wang <syven.wang@sifive.com>
Signed-off-by: Greentime Hu <greentime.hu@sifive.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
[Palmer: Cleaned up the commit text]
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>