[PATCH] RISC-V: mm: Fix set_satp_mode() for platform not having Sv57

[潘庆霖]

Hi Anup,

> 
> We can't assume that it will be the same pgd_index for Sv48 and Sv57.
> 
> For example, some hypothetical SoC might have RAM starting after 1TB space.
> 
> We should ensure that early_pg_dir is cleaned entirely for detecting the next
> mode.
> 

Got it. Your idea is really more stable. Thank you for pointing out that!

Yours,
Qinglin