Add and use a generic version of devmem_is_allowed()

[Luis Chamberlain]

On Thu, Jul 09, 2020 at 02:19:20PM -0700, Palmer Dabbelt wrote:
> As part of adding STRICT_DEVMEM support to the RISC-V port, Zong provided an
> implementation of devmem_is_allowed() that's exactly the same as the version in
> a handful of other ports.  Rather than duplicate code, I've put a generic
> version of this in lib/ and used it for the RISC-V port.
> 
> I've put those first two patches on riscv/for-next, which I'm targeting for 5.9
> (though this is the first version, so they're unreviewed).  The other three
> obviously depend on the first one going on, but I'm not putting them in the
> RISC-V tree as I don't want to step on anyone's toes.  If you want me to take
> yours along with the others then please say something, as otherwise I'll
> probably forget.
> 
> I've put the whole thing at
> ssh://gitolite.kernel.org/pub/scm/linux/kernel/git/palmer/linux.git -b
> generic-devmem .

Reviewed-by: Luis Chamberlain <mcgrof at kernel.org>

  Luis