selftests/memfd: delete unused declarations

Commit 32d118ad ("selftests/memfd: add tests for F_SEAL_EXEC"):
- added several unused 'nbytes' local variables

Commit 6469b66e ("selftests: improve vm.memfd_noexec sysctl tests"):
- orphaned 'newpid_thread_fn2()' forward declaration
- orphaned 'join_newpid_thread()' forward declaration
- added unused 'pid' local in sysctl_simple_child()
- orphaned 'fd' local in sysctl_simple_child()
- added unused 'fd' in sysctl_nested_child()

Delete the unused locals and forward declarations.

Link: https://lkml.kernel.org/r/20240118095057.677544-1-gthelen@google.com


Signed-off-by: Greg Thelen <gthelen@google.com>
Cc: Aleksa Sarai <cyphar@cyphar.com>
Cc: Daniel Verkamp <dverkamp@chromium.org>
Cc: Jeff Xu <jeffxu@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>