testsuite/path: s/__stat64_t64/void/

testsuite/path: s/__stat64_t64/void/

The exact struct varies across the build-options, but in practise is
never __stat64_t64 - this is the internal name used within glibc.

When the fstat declaration with __fstat64_time64 asm linkage is used, we
have "struct stat". Whenever the `#define stat __stat64_time64` kicks
in, both function and struct get redefined/renamed.

Since we don't care about it (apart from the pointer part) just use void.

For more details glibc commit aa03f722f3 ("linux: Add {f}stat{at} y2038
support") added internal.

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Link: https://github.com/kmod-project/kmod/pull/131
Signed-off-by: Lucas De Marchi <lucas.de.marchi@gmail.com>