remove set_fs for riscv v2

[Christoph Hellwig]

Given tht we've not made much progress with the common branch,
are you fine just picking this up through the riscv tree for 5.10?

I'll defer other architectures that depend on the common changes to
5.11 then.

On Wed, Sep 09, 2020 at 08:55:15AM +0200, Christoph Hellwig wrote:
> now that we've sorted out a remaining issue base.set_fs should not
> be rebased any more, so you could pull it into the riscv tree or a topic
> branch.
> 
> The first four patch should go into base.set_fs, though.  Arnd, can you
> re-review the updated patches?
---end quoted text---