futex_wake - Wake some number of threads waiting on a futex.
#include <magenta/syscalls.h>
mx_status_t mx_futex_wake(int* value_ptr, uint32_t wake_count);
Waking a futex causes wake_count threads waiting on the value_ptr
futex to be woken up.
futex_wake() returns NO_ERROR.
futex_wake() always succeeds. Waking up zero threads is not an error condition.