tests: posix: headers: check pthread_spin_lock() et al exist

The simple header test was not updated to verify that the
following functions were implemented even though they were
implemented some time ago.

* pthread_spin_destroy()
* pthread_spin_init()
* pthread_spin_lock()
* pthread_spin_trylock()
* pthread_spin_unlock()

Signed-off-by: Christopher Friedt <cfriedt@meta.com>