selftests/futex: Refactor futex_requeue_pi with kselftest_harness.h

To reduce the boilerplate code, refactor futex_requeue_pi test to use
kselftest_harness header instead of futex's logging header.

Use kselftest fixture feature to make it easy to repeat the same test
with different parameters. With that, drop all repetitive test calls
from run.sh.

Signed-off-by: André Almeida <andrealmeid@igalia.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>