Merge remote-tracking branch 'remotes/vivier2/tags/linux-user-for-5.2-pull-request...

Update syscall numbers to 5.9-rc7
Fixes for prctl(), accept4() and xtensa

# gpg: Signature made Mon 26 Oct 2020 22:02:56 GMT
# gpg:                using RSA key CD2F75DDC8E3A4DC2E4F5173F30C38BD3F2FBE3C
# gpg:                issuer "laurent@vivier.eu"
# gpg: Good signature from "Laurent Vivier <lvivier@redhat.com>" [full]
# gpg:                 aka "Laurent Vivier <laurent@vivier.eu>" [full]
# gpg:                 aka "Laurent Vivier (Red Hat) <lvivier@redhat.com>" [full]
# Primary key fingerprint: CD2F 75DD C8E3 A4DC 2E4F  5173 F30C 38BD 3F2F BE3C

* remotes/vivier2/tags/linux-user-for-5.2-pull-request:
  target/xtensa: enable all coprocessors for linux-user
  linux-user: correct errno returned from accept4() syscall
  linux-user: remove _sysctl
  linux-user: update syscall.tbl to Linux 5.9-rc7
  linux-user: update mips/syscall-args-o32.c.inc to Linux 5.9-rc7
  linux-user: update syscall_nr.h to Linux 5.9-rc7
  linux-user: Support f_flags in statfs64 when available.
  Fix stack smashing when handling PR_GET_PDEATHSIG

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>