futex_wake - Wake some number of threads waiting on a futex.
#include <zircon/syscalls.h>
zx_status_t zx_futex_wake(const zx_futex_t* value_ptr, uint32_t wake_count);
Waking a futex causes wake_count threads waiting on the value_ptr
futex to be woken up.
Waking up zero threads is not an error condition. Passing in an unallocated
address for value_ptr is not an error condition.
futex_wake() returns ZX_OK on success.
ZX_ERR_INVALID_ARGS value_ptr is not aligned.