ntsync: Introduce NTSYNC_IOC_MUTEX_UNLOCK.

This corresponds to the NT syscall NtReleaseMutant().

This syscall decrements the mutex's recursion count by one, and returns the
previous value. If the mutex is not owned by the current task, the function
instead fails and returns -EPERM.

Signed-off-by: Elizabeth Figura <zfigura@codeweavers.com>
Link: https://lore.kernel.org/r/20241213193511.457338-7-zfigura@codeweavers.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>