selftests/mm: remove local __NR_* definitions

selftests/mm: remove local __NR_* definitions

This continues the work on getting the selftests to build without
requiring people to first run "make headers" [1].

Now that the system call numbers are in the correct, checked-in locations
in the kernel tree (./tools/include/uapi/asm/unistd*.h), make sure that
the mm selftests include that file (indirectly).

Doing so provides guaranteed definitions at build time, so remove all of
the checks for "ifdef __NR_xxx" in the mm selftests, because they will
always be true (defined).

[1] commit e076eaca5906 ("selftests: break the dependency upon local
header files")

Link: https://lkml.kernel.org/r/20240618022422.804305-7-jhubbard@nvidia.com
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Jeff Xu <jeffxu@chromium.org>
Cc: Andrei Vagin <avagin@google.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Kees Cook <kees@kernel.org>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Muhammad Usama Anjum <usama.anjum@collabora.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Rich Felker <dalias@libc.org>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>