fix excessive/insufficient wakes in __vm_unlock
fix excessive/insufficient wakes in __vm_unlock

there is no need to send a wake when the lock count does not hit zero,
but when it does, all waiters must be woken (since all with the same
sign are eligible to obtain the lock).

chardi/musl,chardi/musl,davidlazar/musl,davidlazar/musl,chardi/musl