remove set_fs calls from the coredump code v6

[Al Viro]

On Tue, May 05, 2020 at 12:12:49PM +0200, Christoph Hellwig wrote:
> Hi all,
> 
> this series gets rid of playing with the address limit in the exec and
> coredump code.  Most of this was fairly trivial, the biggest changes are
> those to the spufs coredump code.
> 
> Changes since v5:
>  - fix uaccess under spinlock in spufs (Jeremy)
>  - remove use of access_ok in spufs
> 
> Changes since v4:
>  - change some goto names as suggested by Linus
> 
> Changes since v3:
>  - fix x86 compilation with x32 in the new version of the signal code
>  - split the exec patches into a new series
> 
> Changes since v2:
>  - don't cleanup the compat siginfo calling conventions, use the patch
>    variant from Eric with slight coding style fixes instead.
> 
> Changes since v1:
>  - properly spell NUL
>  - properly handle the compat siginfo case in ELF coredumps

Looks good.  Want me to put it into vfs.git?  #work.set_fs-exec, perhaps?