Revert "tests/xstatx.c: fix stat syscall tests on mips64"
Revert "tests/xstatx.c: fix stat syscall tests on mips64"

Previous commit effectively changed types of st_atime, st_ctime, and
st_mtime members of struct stat and struct stat64 to signed integers,
making the mips64 workaround obsolete.

This reverts commit 3fb84bfc79949c145197c61fbf04ce18464e9112.

* tests/xstatx.c (create_sample) [__mips64]: Remove.

cuviper/strace,cuviper/strace,cuviper/strace,cuviper/strace,cuviper/strace